2015-07-29 15:44:57

by Eric B Munson

Subject: [PATCH V6 0/6] Allow user to request memory to be locked on page fault

mlock() allows a user to control page out of program memory, but this
comes at the cost of faulting in the entire mapping when it is
allocated. For large mappings where the entire area is not necessary
this is not ideal. Instead of forcing all locked pages to be present
when they are allocated, this set creates a middle ground. Pages are
marked to be placed on the unevictable LRU (locked) when they are first
used, but they are not faulted in by the mlock call.

This series introduces a new mlock() system call that takes a flags
argument along with the start address and size. This flags argument
gives the caller the ability to request memory be locked in the
traditional way, or to be locked after the page is faulted in. A new
MCL flag is added to mirror the lock on fault behavior from mlock() in
mlockall().

There are two main use cases that this set covers. The first is the
security focussed mlock case. A buffer is needed that cannot be written
to swap. The maximum size is known, but on average the memory used is
significantly less than this maximum. With lock on fault, the buffer
is guaranteed to never be paged out without consuming the maximum size
every time such a buffer is created.

The second use case is focussed on performance. Portions of a large
file are needed and we want to keep the used portions in memory once
accessed. This is the case for large graphical models where the path
through the graph is not known until run time. The entire graph is
unlikely to be used in a given invocation, but once a node has been
used it needs to stay resident for further processing. Given these
constraints we have a number of options. We can potentially waste a
large amount of memory by mlocking the entire region (this can also
cause a significant stall at startup as the entire file is read in).
We can mlock every page as we access them without tracking if the page
is already resident but this introduces large overhead for each access.
The third option is mapping the entire region with PROT_NONE and using
a signal handler for SIGSEGV to mprotect(PROT_READ) and mlock() the
needed page. Doing this page at a time adds a significant performance
penalty. Batching can be used to mitigate this overhead, but in order
to safely avoid trying to mprotect pages outside of the mapping, the
boundaries of each mapping to be used in this way must be tracked and
available to the signal handler. This is precisely what the mm system
in the kernel should already be doing.

For mlock(MLOCK_ONFAULT) the user is charged against RLIMIT_MEMLOCK as
if mlock(MLOCK_LOCKED) or mmap(MAP_LOCKED) was used, so when the VMA is
created not when the pages are faulted in. For mlockall(MCL_ONFAULT)
the user is charged as if MCL_FUTURE was used. This decision was made
to keep the accounting checks out of the page fault path.

To illustrate the benefit of this set I wrote a test program that mmaps
a 5 GB file filled with random data and then makes 15,000,000 accesses
to random addresses in that mapping. The test program was run 20 times
for each setup. Results are reported for two program portions, setup
and execution. The setup phase is calling mmap and optionally mlock on
the entire region. For most experiments this is trivial, but it
highlights the cost of faulting in the entire region. Results are
averages across the 20 runs in milliseconds.

mmap with mlock(MLOCK_LOCKED) on entire range:
Setup avg: 8228.666
Processing avg: 8274.257

mmap with mlock(MLOCK_LOCKED) before each access:
Setup avg: 0.113
Processing avg: 90993.552

mmap with PROT_NONE and signal handler and batch size of 1 page:
With the default value in max_map_count, this gets ENOMEM as I attempt
to change the permissions, after upping the sysctl significantly I get:
Setup avg: 0.058
Processing avg: 69488.073
mmap with PROT_NONE and signal handler and batch size of 8 pages:
Setup avg: 0.068
Processing avg: 38204.116

mmap with PROT_NONE and signal handler and batch size of 16 pages:
Setup avg: 0.044
Processing avg: 29671.180

mmap with mlock(MLOCK_ONFAULT) on entire range:
Setup avg: 0.189
Processing avg: 17904.899

The signal handler in the batch cases faulted in memory in two steps to
avoid having to know the start and end of the faulting mapping. The
first step covers the page that caused the fault as we know that it will
be possible to lock. The second step speculatively tries to mlock and
mprotect the batch size - 1 pages that follow. There may be a clever
way to avoid this without having the program track each mapping to be
covered by this handeler in a globally accessible structure, but I could
not find it. It should be noted that with a large enough batch size
this two step fault handler can still cause the program to crash if it
reaches far beyond the end of the mapping.

These results show that if the developer knows that a majority of the
mapping will be used, it is better to try and fault it in at once,
otherwise mlock(MLOCK_ONFAULT) is significantly faster.

The performance cost of these patches are minimal on the two benchmarks
I have tested (stream and kernbench). The following are the average
values across 20 runs of stream and 10 runs of kernbench after a warmup
run whose results were discarded.

Avg throughput in MB/s from stream using 1000000 element arrays
Test 4.2-rc1 4.2-rc1+lock-on-fault
Copy: 10,566.5 10,421
Scale: 10,685 10,503.5
Add: 12,044.1 11,814.2
Triad: 12,064.8 11,846.3

Kernbench optimal load
4.2-rc1 4.2-rc1+lock-on-fault
Elapsed Time 78.453 78.991
User Time 64.2395 65.2355
System Time 9.7335 9.7085
Context Switches 22211.5 22412.1
Sleeps 14965.3 14956.1

---
Changes from V5:
Drop MLOCK_LOCKED flag
* MLOCK_ONFAULT and MCL_ONFAULT are treated as a modifier to other locking
operations, mirroring the relationship between VM_LOCKED and
VM_LOCKONFAULT
* Drop mmap flag and related tests
* Fix clearing of MCL_CURRENT when mlockall is called with MCL_FUTURE,
mlockall behavoir now matches the old behavior WRT to ordering

Changes from V4:
Drop all architectures for new sys call entries except x86[_64] and MIPS
Drop munlock2 and munlockall2
Make VM_LOCKONFAULT a modifier to VM_LOCKED only to simplify book keeping
Adjust tests to match

Changes from V3:
Ensure that pages present when mlock2(MLOCK_ONFAULT) is called are locked
Ensure that VM_LOCKONFAULT is handled in cases that used to only check VM_LOCKED
Add tests for new system calls
Add missing syscall entries, fix NR_syscalls on multiple arch's
Add missing MAP_LOCKONFAULT for tile

Changes from V2:
Added new system calls for mlock, munlock, and munlockall with added
flags arguments for controlling how memory is locked or unlocked.


Eric B Munson (6):
mm: mlock: Refactor mlock, munlock, and munlockall code
mm: mlock: Add new mlock system call
mm: Introduce VM_LOCKONFAULT
mm: mlock: Add mlock flags to enable VM_LOCKONFAULT usage
selftests: vm: Add tests for lock on fault
mips: Add entry for new mlock2 syscall

arch/alpha/include/uapi/asm/mman.h | 3 +
arch/mips/include/uapi/asm/mman.h | 6 +
arch/mips/include/uapi/asm/unistd.h | 15 +-
arch/mips/kernel/scall32-o32.S | 1 +
arch/mips/kernel/scall64-64.S | 1 +
arch/mips/kernel/scall64-n32.S | 1 +
arch/mips/kernel/scall64-o32.S | 1 +
arch/parisc/include/uapi/asm/mman.h | 3 +
arch/powerpc/include/uapi/asm/mman.h | 1 +
arch/sparc/include/uapi/asm/mman.h | 1 +
arch/tile/include/uapi/asm/mman.h | 1 +
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/xtensa/include/uapi/asm/mman.h | 6 +
drivers/gpu/drm/drm_vm.c | 8 +-
fs/proc/task_mmu.c | 1 +
include/linux/mm.h | 2 +
include/linux/syscalls.h | 2 +
include/uapi/asm-generic/mman-common.h | 5 +
include/uapi/asm-generic/mman.h | 1 +
include/uapi/asm-generic/unistd.h | 4 +-
kernel/fork.c | 2 +-
kernel/sys_ni.c | 1 +
mm/debug.c | 1 +
mm/gup.c | 10 +-
mm/huge_memory.c | 2 +-
mm/hugetlb.c | 4 +-
mm/mlock.c | 91 +++-
mm/mmap.c | 2 +-
mm/rmap.c | 4 +-
tools/testing/selftests/vm/Makefile | 2 +
tools/testing/selftests/vm/mlock2-tests.c | 661 ++++++++++++++++++++++++++++
tools/testing/selftests/vm/on-fault-limit.c | 47 ++
tools/testing/selftests/vm/run_vmtests | 22 +
34 files changed, 873 insertions(+), 41 deletions(-)
create mode 100644 tools/testing/selftests/vm/mlock2-tests.c
create mode 100644 tools/testing/selftests/vm/on-fault-limit.c

Cc: Shuah Khan <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]


--
1.9.1

2015-07-29 15:43:07

by Eric B Munson

Subject: [PATCH V6 1/6] mm: mlock: Refactor mlock, munlock, and munlockall code

Extending the mlock system call is very difficult because it currently
does not take a flags argument. A later patch in this set will extend
mlock to support a middle ground between pages that are locked and
faulted in immediately and unlocked pages. To pave the way for the new
system call, the code needs some reorganization so that all the actual
entry point handles is checking input and translating to VMA flags.

Signed-off-by: Eric B Munson <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
mm/mlock.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index 6fd2cf1..1585cca 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -553,7 +553,8 @@ out:
return ret;
}

-static int do_mlock(unsigned long start, size_t len, int on)
+static int apply_vma_lock_flags(unsigned long start, size_t len,
+ vm_flags_t flags)
{
unsigned long nstart, end, tmp;
struct vm_area_struct * vma, * prev;
@@ -575,14 +576,10 @@ static int do_mlock(unsigned long start, size_t len, int on)
prev = vma;

for (nstart = start ; ; ) {
- vm_flags_t newflags;
+ vm_flags_t newflags = vma->vm_flags & ~VM_LOCKED;
+ newflags |= flags;

/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
-
- newflags = vma->vm_flags & ~VM_LOCKED;
- if (on)
- newflags |= VM_LOCKED;
-
tmp = vma->vm_end;
if (tmp > end)
tmp = end;
@@ -604,7 +601,7 @@ static int do_mlock(unsigned long start, size_t len, int on)
return error;
}

-SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
+static int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
{
unsigned long locked;
unsigned long lock_limit;
@@ -628,7 +625,7 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)

/* check against resource limits */
if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
- error = do_mlock(start, len, 1);
+ error = apply_vma_lock_flags(start, len, flags);

up_write(&current->mm->mmap_sem);
if (error)
@@ -640,6 +637,11 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
return 0;
}

+SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
+{
+ return do_mlock(start, len, VM_LOCKED);
+}
+
SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
int ret;
@@ -648,13 +650,13 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
start &= PAGE_MASK;

down_write(&current->mm->mmap_sem);
- ret = do_mlock(start, len, 0);
+ ret = apply_vma_lock_flags(start, len, 0);
up_write(&current->mm->mmap_sem);

return ret;
}

-static int do_mlockall(int flags)
+static int apply_mlockall_flags(int flags)
{
struct vm_area_struct * vma, * prev = NULL;

@@ -662,6 +664,7 @@ static int do_mlockall(int flags)
current->mm->def_flags |= VM_LOCKED;
else
current->mm->def_flags &= ~VM_LOCKED;
+
if (flags == MCL_FUTURE)
goto out;

@@ -703,7 +706,7 @@ SYSCALL_DEFINE1(mlockall, int, flags)

if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
capable(CAP_IPC_LOCK))
- ret = do_mlockall(flags);
+ ret = apply_mlockall_flags(flags);
up_write(&current->mm->mmap_sem);
if (!ret && (flags & MCL_CURRENT))
mm_populate(0, TASK_SIZE);
@@ -716,7 +719,7 @@ SYSCALL_DEFINE0(munlockall)
int ret;

down_write(&current->mm->mmap_sem);
- ret = do_mlockall(0);
+ ret = apply_mlockall_flags(0);
up_write(&current->mm->mmap_sem);
return ret;
}
--
1.9.1

2015-07-29 15:44:20

by Eric B Munson

Subject: [PATCH V6 2/6] mm: mlock: Add new mlock system call

With the refactored mlock code, introduce a new system call for mlock.
The new call will allow the user to specify what lock states are being
added. mlock2 is trivial at the moment, but a follow on patch will add
a new mlock state making it useful.

Signed-off-by: Eric B Munson <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
include/linux/syscalls.h | 2 ++
include/uapi/asm-generic/unistd.h | 4 +++-
kernel/sys_ni.c | 1 +
mm/mlock.c | 9 +++++++++
6 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index ef8187f..839d5df 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -365,3 +365,4 @@
356 i386 memfd_create sys_memfd_create
357 i386 bpf sys_bpf
358 i386 execveat sys_execveat stub32_execveat
+359 i386 mlock2 sys_mlock2
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 9ef32d5..ad36769 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -329,6 +329,7 @@
320 common kexec_file_load sys_kexec_file_load
321 common bpf sys_bpf
322 64 execveat stub_execveat
+323 common mlock2 sys_mlock2

#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index b45c45b..56a3d59 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -884,4 +884,6 @@ asmlinkage long sys_execveat(int dfd, const char __user *filename,
const char __user *const __user *argv,
const char __user *const __user *envp, int flags);

+asmlinkage long sys_mlock2(unsigned long start, size_t len, int flags);
+
#endif
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index e016bd9..14a6013 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -709,9 +709,11 @@ __SYSCALL(__NR_memfd_create, sys_memfd_create)
__SYSCALL(__NR_bpf, sys_bpf)
#define __NR_execveat 281
__SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat)
+#define __NR_mlock2 282
+__SYSCALL(__NR_mlock2, sys_mlock2)

#undef __NR_syscalls
-#define __NR_syscalls 282
+#define __NR_syscalls 283

/*
* All syscalls below here should go away really,
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 7995ef5..4818b71 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -193,6 +193,7 @@ cond_syscall(sys_mlock);
cond_syscall(sys_munlock);
cond_syscall(sys_mlockall);
cond_syscall(sys_munlockall);
+cond_syscall(sys_mlock2);
cond_syscall(sys_mincore);
cond_syscall(sys_madvise);
cond_syscall(sys_mremap);
diff --git a/mm/mlock.c b/mm/mlock.c
index 1585cca..807f986 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -642,6 +642,15 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
return do_mlock(start, len, VM_LOCKED);
}

+SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
+{
+ vm_flags_t vm_flags = VM_LOCKED;
+ if (flags)
+ return -EINVAL;
+
+ return do_mlock(start, len, vm_flags);
+}
+
SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
int ret;
--
1.9.1

2015-07-29 15:44:22

by Eric B Munson

Subject: [PATCH V6 3/6] mm: Introduce VM_LOCKONFAULT

The cost of faulting in all memory to be locked can be very high when
working with large mappings. If only portions of the mapping will be
used this can incur a high penalty for locking.

For the example of a large file, this is the usage pattern for a large
statical language model (probably applies to other statical or graphical
models as well). For the security example, any application transacting
in data that cannot be swapped out (credit card data, medical records,
etc).

This patch introduces the ability to request that pages are not
pre-faulted, but are placed on the unevictable LRU when they are finally
faulted in. The VM_LOCKONFAULT flag will be used together with
VM_LOCKED and has no effect when set without VM_LOCKED. Setting the
VM_LOCKONFAULT flag for a VMA will cause pages faulted into that VMA to
be added to the unevictable LRU when they are faulted or if they are
already present, but will not cause any missing pages to be faulted in.

Exposing this new lock state means that we cannot overload the meaning
of the FOLL_POPULATE flag any longer. Prior to this patch it was used
to mean that the VMA for a fault was locked. This means we need the
new FOLL_MLOCK flag to communicate the locked state of a VMA.
FOLL_POPULATE will now only control if the VMA should be populated and
in the case of VM_LOCKONFAULT, it will not be set.

Signed-off-by: Eric B Munson <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
drivers/gpu/drm/drm_vm.c | 8 +++++++-
fs/proc/task_mmu.c | 1 +
include/linux/mm.h | 2 ++
kernel/fork.c | 2 +-
mm/debug.c | 1 +
mm/gup.c | 10 ++++++++--
mm/huge_memory.c | 2 +-
mm/hugetlb.c | 4 ++--
mm/mlock.c | 2 +-
mm/mmap.c | 2 +-
mm/rmap.c | 4 ++--
11 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index aab49ee..103a5f6 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -699,9 +699,15 @@ int drm_vma_info(struct seq_file *m, void *data)
(void *)(unsigned long)virt_to_phys(high_memory));

list_for_each_entry(pt, &dev->vmalist, head) {
+ char lock_flag = '-';
+
vma = pt->vma;
if (!vma)
continue;
+ if (vma->vm_flags & VM_LOCKONFAULT)
+ lock_flag = 'f';
+ else if (vma->vm_flags & VM_LOCKED)
+ lock_flag = 'l';
seq_printf(m,
"\n%5d 0x%pK-0x%pK %c%c%c%c%c%c 0x%08lx000",
pt->pid,
@@ -710,7 +716,7 @@ int drm_vma_info(struct seq_file *m, void *data)
vma->vm_flags & VM_WRITE ? 'w' : '-',
vma->vm_flags & VM_EXEC ? 'x' : '-',
vma->vm_flags & VM_MAYSHARE ? 's' : 'p',
- vma->vm_flags & VM_LOCKED ? 'l' : '-',
+ lock_flag,
vma->vm_flags & VM_IO ? 'i' : '-',
vma->vm_pgoff);

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ca1e091..38d69fc 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -579,6 +579,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
#ifdef CONFIG_X86_INTEL_MPX
[ilog2(VM_MPX)] = "mp",
#endif
+ [ilog2(VM_LOCKONFAULT)] = "lf",
[ilog2(VM_LOCKED)] = "lo",
[ilog2(VM_IO)] = "io",
[ilog2(VM_SEQ_READ)] = "sr",
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2e872f9..c2f3551 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -127,6 +127,7 @@ extern unsigned int kobjsize(const void *objp);
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */

+#define VM_LOCKONFAULT 0x00001000 /* Lock the pages covered when they are faulted in */
#define VM_LOCKED 0x00002000
#define VM_IO 0x00004000 /* Memory mapped I/O or similar */

@@ -2043,6 +2044,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
+#define FOLL_MLOCK 0x1000 /* lock present pages */

typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
diff --git a/kernel/fork.c b/kernel/fork.c
index dbd9b8d..a949228 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -454,7 +454,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
tmp->vm_mm = mm;
if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
- tmp->vm_flags &= ~VM_LOCKED;
+ tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file;
if (file) {
diff --git a/mm/debug.c b/mm/debug.c
index 76089dd..25176bb 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -121,6 +121,7 @@ static const struct trace_print_flags vmaflags_names[] = {
{VM_GROWSDOWN, "growsdown" },
{VM_PFNMAP, "pfnmap" },
{VM_DENYWRITE, "denywrite" },
+ {VM_LOCKONFAULT, "lockonfault" },
{VM_LOCKED, "locked" },
{VM_IO, "io" },
{VM_SEQ_READ, "seqread" },
diff --git a/mm/gup.c b/mm/gup.c
index 6297f6b..e632908 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -92,7 +92,7 @@ retry:
*/
mark_page_accessed(page);
}
- if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
/*
* The preliminary mapping check is mainly to avoid the
* pointless overhead of lock_page on the ZERO_PAGE
@@ -265,6 +265,9 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
unsigned int fault_flags = 0;
int ret;

+ /* mlock all present pages, but do not fault in new pages */
+ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
+ return -ENOENT;
/* For mm_populate(), just skip the stack guard page. */
if ((*flags & FOLL_POPULATE) &&
(stack_guard_page_start(vma, address) ||
@@ -850,7 +853,10 @@ long populate_vma_page_range(struct vm_area_struct *vma,
VM_BUG_ON_VMA(end > vma->vm_end, vma);
VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);

- gup_flags = FOLL_TOUCH | FOLL_POPULATE;
+ gup_flags = FOLL_TOUCH | FOLL_MLOCK;
+ if ((vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT)) == VM_LOCKED)
+ gup_flags |= FOLL_POPULATE;
+
/*
* We want to touch writable mappings with a write fault in order
* to break COW, except for shared mappings because these don't COW
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c107094..98ee786 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1238,7 +1238,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
pmd, _pmd, 1))
update_mmu_cache_pmd(vma, addr, pmd);
}
- if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
if (page->mapping && trylock_page(page)) {
lru_add_drain();
if (page->mapping)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a8c3087..82caa48 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3764,8 +3764,8 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma,
unsigned long s_end = sbase + PUD_SIZE;

/* Allow segments to share if only one is marked locked */
- unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
- unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
+ unsigned long vm_flags = vma->vm_flags & ~(VM_LOCKED | VM_LOCKONFAULT);
+ unsigned long svm_flags = svma->vm_flags & ~(VM_LOCKED | VM_LOCKONFAULT);

/*
* match the virtual addresses, permission and the alignment of the
diff --git a/mm/mlock.c b/mm/mlock.c
index 807f986..2a3a860 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -422,7 +422,7 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
- vma->vm_flags &= ~VM_LOCKED;
+ vma->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);

while (start < end) {
struct page *page = NULL;
diff --git a/mm/mmap.c b/mm/mmap.c
index aa632ad..bdbefc3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1651,7 +1651,7 @@ out:
vma == get_gate_vma(current->mm)))
mm->locked_vm += (len >> PAGE_SHIFT);
else
- vma->vm_flags &= ~VM_LOCKED;
+ vma->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
}

if (file)
diff --git a/mm/rmap.c b/mm/rmap.c
index 171b687..47c855a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -744,7 +744,7 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,

if (vma->vm_flags & VM_LOCKED) {
spin_unlock(ptl);
- pra->vm_flags |= VM_LOCKED;
+ pra->vm_flags |= (vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT));
return SWAP_FAIL; /* To break the loop */
}

@@ -765,7 +765,7 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,

if (vma->vm_flags & VM_LOCKED) {
pte_unmap_unlock(pte, ptl);
- pra->vm_flags |= VM_LOCKED;
+ pra->vm_flags |= (vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT));
return SWAP_FAIL; /* To break the loop */
}

--
1.9.1

2015-07-29 15:43:11

by Eric B Munson

Subject: [PATCH V6 4/6] mm: mlock: Add mlock flags to enable VM_LOCKONFAULT usage

The previous patch introduced a flag that specified pages in a VMA
should be placed on the unevictable LRU, but they should not be made
present when the area is created. This patch adds the ability to set
this state via the new mlock system calls.

We add MLOCK_ONFAULT for mlock2 and MCL_ONFAULT for mlockall.
MLOCK_ONFAULT will set the VM_LOCKONFAULT modifier for VM_LOCKED.
MCL_ONFAULT should be used as a modifier to the two other mlockall
flags. When used with MCL_CURRENT, all current mappings will be marked
with VM_LOCKED | VM_LOCKONFAULT. When used with MCL_FUTURE, the
mm->def_flags will be marked with VM_LOCKED | VM_LOCKONFAULT. When used
with both MCL_CURRENT and MCL_FUTURE, all current mappings and
mm->def_flags will be marked with VM_LOCKED | VM_LOCKONFAULT.

Prior to this patch, mlockall() will unconditionally clear the
mm->def_flags any time it is called without MCL_FUTURE. This behavior
is maintained after adding MCL_ONFAULT. If a call to
mlockall(MCL_FUTURE) is followed by mlockall(MCL_CURRENT), the
mm->def_flags will be cleared and new VMAs will be unlocked. This
remains true with or without MCL_ONFAULT in either mlockall()
invocation.

munlock() will unconditionally clear both vma flags. munlockall()
unconditionally clears for VMA flags on all VMAs and in the
mm->def_flags field.

Signed-off-by: Eric B Munson <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
arch/alpha/include/uapi/asm/mman.h | 3 ++
arch/mips/include/uapi/asm/mman.h | 6 ++++
arch/parisc/include/uapi/asm/mman.h | 3 ++
arch/powerpc/include/uapi/asm/mman.h | 1 +
arch/sparc/include/uapi/asm/mman.h | 1 +
arch/tile/include/uapi/asm/mman.h | 1 +
arch/xtensa/include/uapi/asm/mman.h | 6 ++++
include/uapi/asm-generic/mman-common.h | 5 ++++
include/uapi/asm-generic/mman.h | 1 +
mm/mlock.c | 55 ++++++++++++++++++++++++++--------
10 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h
index 0086b47..f2f9496 100644
--- a/arch/alpha/include/uapi/asm/mman.h
+++ b/arch/alpha/include/uapi/asm/mman.h
@@ -37,6 +37,9 @@

#define MCL_CURRENT 8192 /* lock all currently mapped pages */
#define MCL_FUTURE 16384 /* lock all additions to address space */
+#define MCL_ONFAULT 32768 /* lock all pages that are faulted in */
+
+#define MLOCK_ONFAULT 0x01 /* Lock pages in range after they are faulted in, do not prefault */

#define MADV_NORMAL 0 /* no further special treatment */
#define MADV_RANDOM 1 /* expect random page references */
diff --git a/arch/mips/include/uapi/asm/mman.h b/arch/mips/include/uapi/asm/mman.h
index cfcb876..97c03f4 100644
--- a/arch/mips/include/uapi/asm/mman.h
+++ b/arch/mips/include/uapi/asm/mman.h
@@ -61,6 +61,12 @@
*/
#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
+#define MCL_ONFAULT 4 /* lock all pages that are faulted in */
+
+/*
+ * Flags for mlock
+ */
+#define MLOCK_ONFAULT 0x01 /* Lock pages in range after they are faulted in, do not prefault */

#define MADV_NORMAL 0 /* no further special treatment */
#define MADV_RANDOM 1 /* expect random page references */
diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h
index 294d251..ecc3ae1 100644
--- a/arch/parisc/include/uapi/asm/mman.h
+++ b/arch/parisc/include/uapi/asm/mman.h
@@ -31,6 +31,9 @@

#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
+#define MCL_ONFAULT 4 /* lock all pages that are faulted in */
+
+#define MLOCK_ONFAULT 0x01 /* Lock pages in range after they are faulted in, do not prefault */

#define MADV_NORMAL 0 /* no further special treatment */
#define MADV_RANDOM 1 /* expect random page references */
diff --git a/arch/powerpc/include/uapi/asm/mman.h b/arch/powerpc/include/uapi/asm/mman.h
index 6ea26df..03c06ba 100644
--- a/arch/powerpc/include/uapi/asm/mman.h
+++ b/arch/powerpc/include/uapi/asm/mman.h
@@ -22,6 +22,7 @@

#define MCL_CURRENT 0x2000 /* lock all currently mapped pages */
#define MCL_FUTURE 0x4000 /* lock all additions to address space */
+#define MCL_ONFAULT 0x8000 /* lock all pages that are faulted in */

#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
diff --git a/arch/sparc/include/uapi/asm/mman.h b/arch/sparc/include/uapi/asm/mman.h
index 0b14df3..9765896 100644
--- a/arch/sparc/include/uapi/asm/mman.h
+++ b/arch/sparc/include/uapi/asm/mman.h
@@ -17,6 +17,7 @@

#define MCL_CURRENT 0x2000 /* lock all currently mapped pages */
#define MCL_FUTURE 0x4000 /* lock all additions to address space */
+#define MCL_ONFAULT 0x8000 /* lock all pages that are faulted in */

#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
diff --git a/arch/tile/include/uapi/asm/mman.h b/arch/tile/include/uapi/asm/mman.h
index 81b8fc3..63ee13f 100644
--- a/arch/tile/include/uapi/asm/mman.h
+++ b/arch/tile/include/uapi/asm/mman.h
@@ -36,6 +36,7 @@
*/
#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
+#define MCL_ONFAULT 4 /* lock all pages that are faulted in */


#endif /* _ASM_TILE_MMAN_H */
diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
index 201aec0..360944e 100644
--- a/arch/xtensa/include/uapi/asm/mman.h
+++ b/arch/xtensa/include/uapi/asm/mman.h
@@ -74,6 +74,12 @@
*/
#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
+#define MCL_ONFAULT 4 /* lock all pages that are faulted in */
+
+/*
+ * Flags for mlock
+ */
+#define MLOCK_ONFAULT 0x01 /* Lock pages in range after they are faulted in, do not prefault */

#define MADV_NORMAL 0 /* no further special treatment */
#define MADV_RANDOM 1 /* expect random page references */
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index ddc3b36..a74dd84 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h
@@ -25,6 +25,11 @@
# define MAP_UNINITIALIZED 0x0 /* Don't support this flag */
#endif

+/*
+ * Flags for mlock
+ */
+#define MLOCK_ONFAULT 0x01 /* Lock pages in range after they are faulted in, do not prefault */
+
#define MS_ASYNC 1 /* sync memory asynchronously */
#define MS_INVALIDATE 2 /* invalidate the caches */
#define MS_SYNC 4 /* synchronous memory sync */
diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
index e9fe6fd..7162cd4 100644
--- a/include/uapi/asm-generic/mman.h
+++ b/include/uapi/asm-generic/mman.h
@@ -17,5 +17,6 @@

#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */
+#define MCL_ONFAULT 4 /* lock all pages that are faulted in */

#endif /* __ASM_GENERIC_MMAN_H */
diff --git a/mm/mlock.c b/mm/mlock.c
index 2a3a860..5eeeb83 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -506,7 +506,8 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,

if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
- goto out; /* don't set VM_LOCKED, don't count */
+ /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
+ goto out;

pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
@@ -576,7 +577,7 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
prev = vma;

for (nstart = start ; ; ) {
- vm_flags_t newflags = vma->vm_flags & ~VM_LOCKED;
+ vm_flags_t newflags = vma->vm_flags & ~(VM_LOCKED | VM_LOCKONFAULT);
newflags |= flags;

/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
@@ -645,9 +646,12 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
{
vm_flags_t vm_flags = VM_LOCKED;
- if (flags)
+ if (flags & ~MLOCK_ONFAULT)
return -EINVAL;

+ if (flags & MLOCK_ONFAULT)
+ vm_flags |= VM_LOCKONFAULT;
+
return do_mlock(start, len, vm_flags);
}

@@ -665,24 +669,50 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
return ret;
}

+/*
+ * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
+ * and translate into the appropriate modifications to mm->def_flags and/or the
+ * flags for all current VMAs.
+ *
+ * There are a couple of sublties with this. If mlockall() is called multiple
+ * times with different flags, the values do not necessarily stack. If mlockall
+ * is called once including the MCL_FUTURE flag and then a second time without
+ * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
+ */
static int apply_mlockall_flags(int flags)
{
struct vm_area_struct * vma, * prev = NULL;
+ vm_flags_t to_add = 0;

- if (flags & MCL_FUTURE)
+ current->mm->def_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
+ if (flags & MCL_FUTURE) {
current->mm->def_flags |= VM_LOCKED;
- else
- current->mm->def_flags &= ~VM_LOCKED;

- if (flags == MCL_FUTURE)
- goto out;
+ if (flags & MCL_ONFAULT)
+ current->mm->def_flags |= VM_LOCKONFAULT;
+
+ /*
+ * When there were only two flags, we used to early out if only
+ * MCL_FUTURE was set. Now that we have MCL_ONFAULT, we can
+ * only early out if MCL_FUTURE is set, but MCL_CURRENT is not.
+ * This is done, even though it promotes odd behavior, to
+ * maintain behavior from older kernels
+ */
+ if (!(flags & MCL_CURRENT))
+ goto out;
+ }
+
+ if (flags & MCL_CURRENT) {
+ to_add |= VM_LOCKED;
+ if (flags & MCL_ONFAULT)
+ to_add |= VM_LOCKONFAULT;
+ }

for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
vm_flags_t newflags;

- newflags = vma->vm_flags & ~VM_LOCKED;
- if (flags & MCL_CURRENT)
- newflags |= VM_LOCKED;
+ newflags = vma->vm_flags & ~(VM_LOCKED | VM_LOCKONFAULT);
+ newflags |= to_add;

/* Ignore errors */
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
@@ -697,7 +727,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
unsigned long lock_limit;
int ret = -EINVAL;

- if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
+ if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
+ flags == MCL_ONFAULT)
goto out;

ret = -EPERM;
--
1.9.1

2015-07-29 15:43:15

by Eric B Munson

Subject: [PATCH V6 5/6] selftests: vm: Add tests for lock on fault

Test the mlockall() flag and the mlock2 system call. These tests ensure
that pages are not faulted in until they are accessed, that the pages
are unevictable once faulted in, and that VMA splitting and merging
works with the new VM flag. The second test ensures that mlock limits
are respected. Note that the limit test needs to be run a normal user.

Also add tests to use the new mlock2 family of system calls.

Signed-off-by: Eric B Munson <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
tools/testing/selftests/vm/Makefile | 2 +
tools/testing/selftests/vm/mlock2-tests.c | 661 ++++++++++++++++++++++++++++
tools/testing/selftests/vm/on-fault-limit.c | 47 ++
tools/testing/selftests/vm/run_vmtests | 22 +
4 files changed, 732 insertions(+)
create mode 100644 tools/testing/selftests/vm/mlock2-tests.c
create mode 100644 tools/testing/selftests/vm/on-fault-limit.c

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 231b9a0..71a4e9f 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -6,6 +6,8 @@ BINARIES += hugepage-mmap
BINARIES += hugepage-shm
BINARIES += hugetlbfstest
BINARIES += map_hugetlb
+BINARIES += mlock2-tests
+BINARIES += on-fault-limit
BINARIES += thuge-gen
BINARIES += transhuge-stress

diff --git a/tools/testing/selftests/vm/mlock2-tests.c b/tools/testing/selftests/vm/mlock2-tests.c
new file mode 100644
index 0000000..c49122b
--- /dev/null
+++ b/tools/testing/selftests/vm/mlock2-tests.c
@@ -0,0 +1,661 @@
+#include <sys/mman.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <errno.h>
+#include <stdbool.h>
+
+#ifndef MLOCK_ONFAULT
+#define MLOCK_ONFAULT 1
+#endif
+
+#ifndef MCL_ONFAULT
+#define MCL_ONFAULT (MCL_FUTURE << 1)
+#endif
+
+static int mlock2_(void *start, size_t len, int flags)
+{
+#ifdef __NR_mlock2
+ return syscall(__NR_mlock2, start, len, flags);
+#else
+ errno = ENOSYS;
+ return -1;
+#endif
+}
+
+struct vm_boundaries {
+ unsigned long start;
+ unsigned long end;
+};
+
+static int get_vm_area(unsigned long addr, struct vm_boundaries *area)
+{
+ FILE *file;
+ int ret = 1;
+ char line[1024] = {0};
+ char *end_addr;
+ char *stop;
+ unsigned long start;
+ unsigned long end;
+
+ if (!area)
+ return ret;
+
+ file = fopen("/proc/self/maps", "r");
+ if (!file) {
+ perror("fopen");
+ return ret;
+ }
+
+ memset(area, 0, sizeof(struct vm_boundaries));
+
+ while(fgets(line, 1024, file)) {
+ end_addr = strchr(line, '-');
+ if (!end_addr) {
+ printf("cannot parse /proc/self/maps\n");
+ goto out;
+ }
+ *end_addr = '\0';
+ end_addr++;
+ stop = strchr(end_addr, ' ');
+ if (!stop) {
+ printf("cannot parse /proc/self/maps\n");
+ goto out;
+ }
+ stop = '\0';
+
+ sscanf(line, "%lx", &start);
+ sscanf(end_addr, "%lx", &end);
+
+ if (start <= addr && end > addr) {
+ area->start = start;
+ area->end = end;
+ ret = 0;
+ goto out;
+ }
+ }
+out:
+ fclose(file);
+ return ret;
+}
+
+static unsigned long get_pageflags(unsigned long addr)
+{
+ FILE *file;
+ unsigned long pfn;
+ unsigned long offset;
+
+ file = fopen("/proc/self/pagemap", "r");
+ if (!file) {
+ perror("fopen pagemap");
+ _exit(1);
+ }
+
+ offset = addr / getpagesize() * sizeof(unsigned long);
+ if (fseek(file, offset, SEEK_SET)) {
+ perror("fseek pagemap");
+ _exit(1);
+ }
+
+ if (fread(&pfn, sizeof(unsigned long), 1, file) != 1) {
+ perror("fread pagemap");
+ _exit(1);
+ }
+
+ fclose(file);
+ return pfn;
+}
+
+static unsigned long get_kpageflags(unsigned long pfn)
+{
+ unsigned long flags;
+ FILE *file;
+
+ file = fopen("/proc/kpageflags", "r");
+ if (!file) {
+ perror("fopen kpageflags");
+ _exit(1);
+ }
+
+ if (fseek(file, pfn * sizeof(unsigned long), SEEK_SET)) {
+ perror("fseek kpageflags");
+ _exit(1);
+ }
+
+ if (fread(&flags, sizeof(unsigned long), 1, file) != 1) {
+ perror("fread kpageflags");
+ _exit(1);
+ }
+
+ fclose(file);
+ return flags;
+}
+
+#define VMFLAGS "VmFlags:"
+
+static bool find_flag(FILE *file, const char *vmflag)
+{
+ char *line = NULL;
+ char *flags;
+ size_t size = 0;
+ bool ret = false;
+
+ while (getline(&line, &size, file) > 0) {
+ if (!strstr(line, VMFLAGS)) {
+ free(line);
+ line = NULL;
+ size = 0;
+ continue;
+ }
+
+ flags = line + strlen(VMFLAGS);
+ ret = (strstr(flags, vmflag) != NULL);
+ goto out;
+ }
+
+out:
+ free(line);
+ return ret;
+}
+
+static bool is_vmflag_set(unsigned long addr, const char *vmflag)
+{
+ FILE *file;
+ char *line = NULL;
+ size_t size = 0;
+ bool ret = false;
+ unsigned long start, end;
+ char perms[5];
+ unsigned long offset;
+ char dev[32];
+ unsigned long inode;
+ char path[BUFSIZ];
+
+ file = fopen("/proc/self/smaps", "r");
+ if (!file) {
+ perror("fopen smaps");
+ _exit(1);
+ }
+
+ while (getline(&line, &size, file) > 0) {
+ if (sscanf(line, "%lx-%lx %s %lx %s %lu %s\n",
+ &start, &end, perms, &offset, dev, &inode, path) < 6)
+ goto next;
+
+ if (start <= addr && addr < end) {
+ ret = find_flag(file, vmflag);
+ goto out;
+ }
+
+next:
+ free(line);
+ line = NULL;
+ size = 0;
+ }
+
+out:
+ free(line);
+ fclose(file);
+ return ret;
+}
+
+#define PRESENT_BIT 0x8000000000000000
+#define PFN_MASK 0x007FFFFFFFFFFFFF
+#define UNEVICTABLE_BIT (1UL << 18)
+
+#define LOCKED "lo"
+#define LOCKEDONFAULT "lf"
+
+static int lock_check(char *map)
+{
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ page1_flags = get_pageflags((unsigned long)map);
+ page2_flags = get_pageflags((unsigned long)map + page_size);
+
+ /* Both pages should be present */
+ if (((page1_flags & PRESENT_BIT) == 0) ||
+ ((page2_flags & PRESENT_BIT) == 0)) {
+ printf("Failed to make both pages present\n");
+ return 1;
+ }
+
+ page1_flags = get_kpageflags(page1_flags & PFN_MASK);
+ page2_flags = get_kpageflags(page2_flags & PFN_MASK);
+
+ /* Both pages should be unevictable */
+ if (((page1_flags & UNEVICTABLE_BIT) == 0) ||
+ ((page2_flags & UNEVICTABLE_BIT) == 0)) {
+ printf("Failed to make both pages unevictable\n");
+ return 1;
+ }
+
+ if (!is_vmflag_set((unsigned long)map, LOCKED) ||
+ !is_vmflag_set((unsigned long)map + page_size, LOCKED)) {
+ printf("VMA flag %s is missing\n", LOCKED);
+ return 1;
+ }
+
+ return 0;
+}
+
+static int unlock_lock_check(char *map)
+{
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ page1_flags = get_pageflags((unsigned long)map);
+ page2_flags = get_pageflags((unsigned long)map + page_size);
+ page1_flags = get_kpageflags(page1_flags & PFN_MASK);
+ page2_flags = get_kpageflags(page2_flags & PFN_MASK);
+
+ if ((page1_flags & UNEVICTABLE_BIT) || (page2_flags & UNEVICTABLE_BIT)) {
+ printf("A page is still marked unevictable after unlock\n");
+ return 1;
+ }
+
+ if (is_vmflag_set((unsigned long)map, LOCKED) ||
+ is_vmflag_set((unsigned long)map + page_size, LOCKED)) {
+ printf("VMA flag %s is still set after unlock\n", LOCKED);
+ return 1;
+ }
+
+ return 0;
+}
+
+static int test_mlock_lock()
+{
+ char *map;
+ int ret = 1;
+ unsigned long page_size = getpagesize();
+
+ map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+ if (map == MAP_FAILED) {
+ perror("test_mlock_locked mmap");
+ goto out;
+ }
+
+ if (mlock2_(map, 2 * page_size, 0)) {
+ if (errno == ENOSYS) {
+ printf("Cannot call new mlock family, skipping test\n");
+ _exit(0);
+ }
+ perror("mlock2(0)");
+ goto unmap;
+ }
+
+ if (lock_check(map))
+ goto unmap;
+
+ /* Now unlock and recheck attributes */
+ if (munlock(map, 2 * page_size)) {
+ perror("munlock()");
+ goto unmap;
+ }
+
+ ret = unlock_lock_check(map);
+
+unmap:
+ munmap(map, 2 * page_size);
+out:
+ return ret;
+}
+
+static int onfault_check(char *map)
+{
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ page1_flags = get_pageflags((unsigned long)map);
+ page2_flags = get_pageflags((unsigned long)map + page_size);
+
+ /* Neither page should be present */
+ if ((page1_flags & PRESENT_BIT) || (page2_flags & PRESENT_BIT)) {
+ printf("Pages were made present by MLOCK_ONFAULT\n");
+ return 1;
+ }
+
+ *map = 'a';
+ page1_flags = get_pageflags((unsigned long)map);
+ page2_flags = get_pageflags((unsigned long)map + page_size);
+
+ /* Only page 1 should be present */
+ if ((page1_flags & PRESENT_BIT) == 0) {
+ printf("Page 1 is not present after fault\n");
+ return 1;
+ } else if (page2_flags & PRESENT_BIT) {
+ printf("Page 2 was made present\n");
+ return 1;
+ }
+
+ page1_flags = get_kpageflags(page1_flags & PFN_MASK);
+
+ /* Page 1 should be unevictable */
+ if ((page1_flags & UNEVICTABLE_BIT) == 0) {
+ printf("Failed to make faulted page unevictable\n");
+ return 1;
+ }
+
+ if (!is_vmflag_set((unsigned long)map, LOCKEDONFAULT) ||
+ !is_vmflag_set((unsigned long)map + page_size, LOCKEDONFAULT)) {
+ printf("VMA flag %s is missing\n", LOCKEDONFAULT);
+ return 1;
+ }
+
+ return 0;
+}
+
+static int unlock_onfault_check(char *map)
+{
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ page1_flags = get_pageflags((unsigned long)map);
+ page1_flags = get_kpageflags(page1_flags & PFN_MASK);
+
+ if (page1_flags & UNEVICTABLE_BIT) {
+ printf("Page 1 is still marked unevictable after unlock\n");
+ return 1;
+ }
+
+ if (is_vmflag_set((unsigned long)map, LOCKEDONFAULT) ||
+ is_vmflag_set((unsigned long)map + page_size, LOCKEDONFAULT)) {
+ printf("VMA flag %s is still set after unlock\n", LOCKEDONFAULT);
+ return 1;
+ }
+
+ return 0;
+}
+
+static int test_mlock_onfault()
+{
+ char *map;
+ int ret = 1;
+ unsigned long page_size = getpagesize();
+
+ map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+ if (map == MAP_FAILED) {
+ perror("test_mlock_locked mmap");
+ goto out;
+ }
+
+ if (mlock2_(map, 2 * page_size, MLOCK_ONFAULT)) {
+ if (errno == ENOSYS) {
+ printf("Cannot call new mlock family, skipping test\n");
+ _exit(0);
+ }
+ perror("mlock2(MLOCK_ONFAULT)");
+ goto unmap;
+ }
+
+ if (onfault_check(map))
+ goto unmap;
+
+ /* Now unlock and recheck attributes */
+ if (munlock(map, 2 * page_size)) {
+ if (errno == ENOSYS) {
+ printf("Cannot call new mlock family, skipping test\n");
+ _exit(0);
+ }
+ perror("munlock()");
+ goto unmap;
+ }
+
+ ret = unlock_onfault_check(map);
+unmap:
+ munmap(map, 2 * page_size);
+out:
+ return ret;
+}
+
+static int test_lock_onfault_of_present()
+{
+ char *map;
+ int ret = 1;
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+ if (map == MAP_FAILED) {
+ perror("test_mlock_locked mmap");
+ goto out;
+ }
+
+ *map = 'a';
+
+ if (mlock2_(map, 2 * page_size, MLOCK_ONFAULT)) {
+ if (errno == ENOSYS) {
+ printf("Cannot call new mlock family, skipping test\n");
+ _exit(0);
+ }
+ perror("mlock2(MLOCK_ONFAULT)");
+ goto unmap;
+ }
+
+ page1_flags = get_pageflags((unsigned long)map);
+ page2_flags = get_pageflags((unsigned long)map + page_size);
+ page1_flags = get_kpageflags(page1_flags & PFN_MASK);
+ page2_flags = get_kpageflags(page2_flags & PFN_MASK);
+
+ /* Page 1 should be unevictable */
+ if ((page1_flags & UNEVICTABLE_BIT) == 0) {
+ printf("Failed to make present page unevictable\n");
+ goto unmap;
+ }
+
+ if (!is_vmflag_set((unsigned long)map, LOCKEDONFAULT) ||
+ !is_vmflag_set((unsigned long)map + page_size, LOCKEDONFAULT)) {
+ printf("VMA flag %s is missing for one of the pages\n", LOCKEDONFAULT);
+ goto unmap;
+ }
+ ret = 0;
+unmap:
+ munmap(map, 2 * page_size);
+out:
+ return ret;
+}
+
+static int test_munlockall()
+{
+ char *map;
+ int ret = 1;
+ unsigned long page1_flags;
+ unsigned long page2_flags;
+ unsigned long page_size = getpagesize();
+
+ map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+
+ if (map == MAP_FAILED) {
+ perror("test_munlockall mmap");
+ goto out;
+ }
+
+ if (mlockall(MCL_CURRENT)) {
+ perror("mlockall(MCL_CURRENT)");
+ goto out;
+ }
+
+ if (lock_check(map))
+ goto unmap;
+
+ if (munlockall()) {
+ perror("munlockall()");
+ goto unmap;
+ }
+
+ if (unlock_lock_check(map))
+ goto unmap;
+
+ munmap(map, 2 * page_size);
+
+ map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+
+ if (map == MAP_FAILED) {
+ perror("test_munlockall second mmap");
+ goto out;
+ }
+
+ if (mlockall(MCL_CURRENT | MCL_ONFAULT)) {
+ perror("mlockall(MCL_CURRENT | MCL_ONFAULT)");
+ goto unmap;
+ }
+
+ if (onfault_check(map))
+ goto unmap;
+
+ if (munlockall()) {
+ perror("munlockall()");
+ goto unmap;
+ }
+
+ if (unlock_onfault_check(map))
+ goto unmap;
+
+ if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
+ perror("mlockall(MCL_CURRENT | MCL_FUTURE)");
+ goto out;
+ }
+
+ if (lock_check(map))
+ goto unmap;
+
+ if (munlockall()) {
+ perror("munlockall()");
+ goto unmap;
+ }
+
+ ret = unlock_lock_check(map);
+
+unmap:
+ munmap(map, 2 * page_size);
+out:
+ munlockall();
+ return ret;
+}
+
+static int test_vma_management(bool call_mlock)
+{
+ int ret = 1;
+ void *map;
+ unsigned long page_size = getpagesize();
+ struct vm_boundaries page1;
+ struct vm_boundaries page2;
+ struct vm_boundaries page3;
+
+ map = mmap(NULL, 3 * page_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+ if (map == MAP_FAILED) {
+ perror("mmap()");
+ return ret;
+ }
+
+ if (call_mlock && mlock2_(map, 3 * page_size, MLOCK_ONFAULT)) {
+ if (errno == ENOSYS) {
+ printf("Cannot call new mlock family, skipping test\n");
+ _exit(0);
+ }
+ perror("mlock(ONFAULT)\n");
+ goto out;
+ }
+
+ if (get_vm_area((unsigned long)map, &page1) ||
+ get_vm_area((unsigned long)map + page_size, &page2) ||
+ get_vm_area((unsigned long)map + page_size * 2, &page3)) {
+ printf("couldn't find mapping in /proc/self/maps\n");
+ goto out;
+ }
+
+ /*
+ * Before we unlock a portion, we need to that all three pages are in
+ * the same VMA. If they are not we abort this test (Note that this is
+ * not a failure)
+ */
+ if (page1.start != page2.start || page2.start != page3.start) {
+ printf("VMAs are not merged to start, aborting test\n");
+ ret = 0;
+ goto out;
+ }
+
+ if (munlock(map + page_size, page_size)) {
+ perror("munlock()");
+ goto out;
+ }
+
+ if (get_vm_area((unsigned long)map, &page1) ||
+ get_vm_area((unsigned long)map + page_size, &page2) ||
+ get_vm_area((unsigned long)map + page_size * 2, &page3)) {
+ printf("couldn't find mapping in /proc/self/maps\n");
+ goto out;
+ }
+
+ /* All three VMAs should be different */
+ if (page1.start == page2.start || page2.start == page3.start) {
+ printf("failed to split VMA for munlock\n");
+ goto out;
+ }
+
+ /* Now unlock the first and third page and check the VMAs again */
+ if (munlock(map, page_size * 3)) {
+ perror("munlock()");
+ goto out;
+ }
+
+ if (get_vm_area((unsigned long)map, &page1) ||
+ get_vm_area((unsigned long)map + page_size, &page2) ||
+ get_vm_area((unsigned long)map + page_size * 2, &page3)) {
+ printf("couldn't find mapping in /proc/self/maps\n");
+ goto out;
+ }
+
+ /* Now all three VMAs should be the same */
+ if (page1.start != page2.start || page2.start != page3.start) {
+ printf("failed to merge VMAs after munlock\n");
+ goto out;
+ }
+
+ ret = 0;
+out:
+ munmap(map, 3 * page_size);
+ return ret;
+}
+
+static int test_mlockall(int (test_function)(bool call_mlock))
+{
+ int ret = 1;
+
+ if (mlockall(MCL_CURRENT | MCL_ONFAULT | MCL_FUTURE)) {
+ perror("mlockall");
+ return ret;
+ }
+
+ ret = test_function(false);
+ munlockall();
+ return ret;
+}
+
+int main(char **argv, int argc)
+{
+ int ret = 0;
+ ret += test_mlock_lock();
+ ret += test_mlock_onfault();
+ ret += test_munlockall();
+ ret += test_lock_onfault_of_present();
+ ret += test_vma_management(true);
+ ret += test_mlockall(test_vma_management);
+ return ret;
+}
+
diff --git a/tools/testing/selftests/vm/on-fault-limit.c b/tools/testing/selftests/vm/on-fault-limit.c
new file mode 100644
index 0000000..245accc
--- /dev/null
+++ b/tools/testing/selftests/vm/on-fault-limit.c
@@ -0,0 +1,47 @@
+#include <sys/mman.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+
+#ifndef MCL_ONFAULT
+#define MCL_ONFAULT (MCL_FUTURE << 1)
+#endif
+
+static int test_limit(void)
+{
+ int ret = 1;
+ struct rlimit lims;
+ void *map;
+
+ if (getrlimit(RLIMIT_MEMLOCK, &lims)) {
+ perror("getrlimit");
+ return ret;
+ }
+
+ if (mlockall(MCL_CURRENT | MCL_ONFAULT | MCL_FUTURE)) {
+ perror("mlockall");
+ return ret;
+ }
+
+ map = mmap(NULL, 2 * lims.rlim_max, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE, 0, 0);
+ if (map != MAP_FAILED)
+ printf("mmap should have failed, but didn't\n");
+ else {
+ ret = 0;
+ munmap(map, 2 * lims.rlim_max);
+ }
+
+ munlockall();
+ return ret;
+}
+
+int main(int argc, char **argv)
+{
+ int ret = 0;
+
+ ret += test_limit();
+ return ret;
+}
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index 49ece11..877ca04a 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -102,4 +102,26 @@ else
echo "[PASS]"
fi

+echo "--------------------"
+echo "running on-fault-limit"
+echo "--------------------"
+sudo -u nobody ./on-fault-limit
+if [ $? -ne 0 ]; then
+ echo "[FAIL]"
+ exitcode=1
+else
+ echo "[PASS]"
+fi
+
+echo "--------------------"
+echo "running mlock2-tests"
+echo "--------------------"
+./mlock2-tests
+if [ $? -ne 0 ]; then
+ echo "[FAIL]"
+ exitcode=1
+else
+ echo "[PASS]"
+fi
+
exit $exitcode
--
1.9.1

2015-07-29 15:43:13

by Eric B Munson

Subject: [PATCH V6 6/6] mips: Add entry for new mlock2 syscall

A previous commit introduced the new mlock2 syscall, add entries for the
MIPS architecture.

Signed-off-by: Eric B Munson <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
arch/mips/include/uapi/asm/unistd.h | 15 +++++++++------
arch/mips/kernel/scall32-o32.S | 1 +
arch/mips/kernel/scall64-64.S | 1 +
arch/mips/kernel/scall64-n32.S | 1 +
arch/mips/kernel/scall64-o32.S | 1 +
5 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/mips/include/uapi/asm/unistd.h b/arch/mips/include/uapi/asm/unistd.h
index c03088f..d0bdfaa 100644
--- a/arch/mips/include/uapi/asm/unistd.h
+++ b/arch/mips/include/uapi/asm/unistd.h
@@ -377,16 +377,17 @@
#define __NR_memfd_create (__NR_Linux + 354)
#define __NR_bpf (__NR_Linux + 355)
#define __NR_execveat (__NR_Linux + 356)
+#define __NR_mlock2 (__NR_Linux + 357)

/*
* Offset of the last Linux o32 flavoured syscall
*/
-#define __NR_Linux_syscalls 356
+#define __NR_Linux_syscalls 357

#endif /* _MIPS_SIM == _MIPS_SIM_ABI32 */

#define __NR_O32_Linux 4000
-#define __NR_O32_Linux_syscalls 356
+#define __NR_O32_Linux_syscalls 357

#if _MIPS_SIM == _MIPS_SIM_ABI64

@@ -711,16 +712,17 @@
#define __NR_memfd_create (__NR_Linux + 314)
#define __NR_bpf (__NR_Linux + 315)
#define __NR_execveat (__NR_Linux + 316)
+#define __NR_mlock2 (__NR_Linux + 317)

/*
* Offset of the last Linux 64-bit flavoured syscall
*/
-#define __NR_Linux_syscalls 316
+#define __NR_Linux_syscalls 317

#endif /* _MIPS_SIM == _MIPS_SIM_ABI64 */

#define __NR_64_Linux 5000
-#define __NR_64_Linux_syscalls 316
+#define __NR_64_Linux_syscalls 317

#if _MIPS_SIM == _MIPS_SIM_NABI32

@@ -1049,15 +1051,16 @@
#define __NR_memfd_create (__NR_Linux + 318)
#define __NR_bpf (__NR_Linux + 319)
#define __NR_execveat (__NR_Linux + 320)
+#define __NR_mlock2 (__NR_Linux + 321)

/*
* Offset of the last N32 flavoured syscall
*/
-#define __NR_Linux_syscalls 320
+#define __NR_Linux_syscalls 321

#endif /* _MIPS_SIM == _MIPS_SIM_NABI32 */

#define __NR_N32_Linux 6000
-#define __NR_N32_Linux_syscalls 320
+#define __NR_N32_Linux_syscalls 321

#endif /* _UAPI_ASM_UNISTD_H */
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index 4cc1350..b0b377a 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -599,3 +599,4 @@ EXPORT(sys_call_table)
PTR sys_memfd_create
PTR sys_bpf /* 4355 */
PTR sys_execveat
+ PTR sys_mlock2
diff --git a/arch/mips/kernel/scall64-64.S b/arch/mips/kernel/scall64-64.S
index ad4d4463..97aaf51 100644
--- a/arch/mips/kernel/scall64-64.S
+++ b/arch/mips/kernel/scall64-64.S
@@ -436,4 +436,5 @@ EXPORT(sys_call_table)
PTR sys_memfd_create
PTR sys_bpf /* 5315 */
PTR sys_execveat
+ PTR sys_mlock2
.size sys_call_table,.-sys_call_table
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index 446cc65..e36f21e 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -429,4 +429,5 @@ EXPORT(sysn32_call_table)
PTR sys_memfd_create
PTR sys_bpf
PTR compat_sys_execveat /* 6320 */
+ PTR sys_mlock2
.size sysn32_call_table,.-sysn32_call_table
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index f543ff4..7a8b2df 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -584,4 +584,5 @@ EXPORT(sys32_call_table)
PTR sys_memfd_create
PTR sys_bpf /* 4355 */
PTR compat_sys_execveat
+ PTR sys_mlock2
.size sys32_call_table,.-sys32_call_table
--
1.9.1

2015-07-30 14:33:00

by Ralf Baechle

Subject: Re: [PATCH V6 6/6] mips: Add entry for new mlock2 syscall

On Wed, Jul 29, 2015 at 11:42:55AM -0400, Eric B Munson wrote:

> A previous commit introduced the new mlock2 syscall, add entries for the
> MIPS architecture.

Looking good, so

Acked-by: Ralf Baechle <[email protected]>

Recently somebody else was floating around a patch that was adding
three syscalls. Not sure if in the end the adding the syscall part to
non-x86 was dropped. Just mentioning in case there are any conflicts;
in particulary nobody should rely on syscall numbers unless they're
for something in Linus' tree!

Ralf

2015-08-06 13:56:21

by Vlastimil Babka

Subject: Re: [PATCH V6 1/6] mm: mlock: Refactor mlock, munlock, and munlockall code

On 07/29/2015 05:42 PM, Eric B Munson wrote:
> Extending the mlock system call is very difficult because it currently
> does not take a flags argument. A later patch in this set will extend
> mlock to support a middle ground between pages that are locked and
> faulted in immediately and unlocked pages. To pave the way for the new
> system call, the code needs some reorganization so that all the actual
> entry point handles is checking input and translating to VMA flags.
>
> Signed-off-by: Eric B Munson <[email protected]>
> Acked-by: Kirill A. Shutemov <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Vlastimil Babka <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

2015-08-06 14:00:48

by Vlastimil Babka

Subject: Re: [PATCH V6 2/6] mm: mlock: Add new mlock system call

On 07/29/2015 05:42 PM, Eric B Munson wrote:
> With the refactored mlock code, introduce a new system call for mlock.
> The new call will allow the user to specify what lock states are being
> added. mlock2 is trivial at the moment, but a follow on patch will add
> a new mlock state making it useful.
>
> Signed-off-by: Eric B Munson <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Vlastimil Babka <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

2015-08-06 15:34:06

by Vlastimil Babka

Subject: Re: [PATCH V6 3/6] mm: Introduce VM_LOCKONFAULT

On 07/29/2015 05:42 PM, Eric B Munson wrote:
> The cost of faulting in all memory to be locked can be very high when
> working with large mappings. If only portions of the mapping will be
> used this can incur a high penalty for locking.
>
> For the example of a large file, this is the usage pattern for a large
> statical language model (probably applies to other statical or graphical
> models as well). For the security example, any application transacting
> in data that cannot be swapped out (credit card data, medical records,
> etc).
>
> This patch introduces the ability to request that pages are not
> pre-faulted, but are placed on the unevictable LRU when they are finally
> faulted in. The VM_LOCKONFAULT flag will be used together with
> VM_LOCKED and has no effect when set without VM_LOCKED. Setting the
> VM_LOCKONFAULT flag for a VMA will cause pages faulted into that VMA to
> be added to the unevictable LRU when they are faulted or if they are
> already present, but will not cause any missing pages to be faulted in.
>
> Exposing this new lock state means that we cannot overload the meaning
> of the FOLL_POPULATE flag any longer. Prior to this patch it was used
> to mean that the VMA for a fault was locked. This means we need the
> new FOLL_MLOCK flag to communicate the locked state of a VMA.
> FOLL_POPULATE will now only control if the VMA should be populated and
> in the case of VM_LOCKONFAULT, it will not be set.
>
> Signed-off-by: Eric B Munson <[email protected]>
> Acked-by: Kirill A. Shutemov <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Vlastimil Babka <[email protected]>
> Cc: Jonathan Corbet <[email protected]>
> Cc: "Kirill A. Shutemov" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> drivers/gpu/drm/drm_vm.c | 8 +++++++-
> fs/proc/task_mmu.c | 1 +
> include/linux/mm.h | 2 ++
> kernel/fork.c | 2 +-
> mm/debug.c | 1 +
> mm/gup.c | 10 ++++++++--
> mm/huge_memory.c | 2 +-
> mm/hugetlb.c | 4 ++--
> mm/mlock.c | 2 +-
> mm/mmap.c | 2 +-
> mm/rmap.c | 4 ++--
> 11 files changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
> index aab49ee..103a5f6 100644
> --- a/drivers/gpu/drm/drm_vm.c
> +++ b/drivers/gpu/drm/drm_vm.c
> @@ -699,9 +699,15 @@ int drm_vma_info(struct seq_file *m, void *data)
> (void *)(unsigned long)virt_to_phys(high_memory));
>
> list_for_each_entry(pt, &dev->vmalist, head) {
> + char lock_flag = '-';
> +
> vma = pt->vma;
> if (!vma)
> continue;
> + if (vma->vm_flags & VM_LOCKONFAULT)
> + lock_flag = 'f';
> + else if (vma->vm_flags & VM_LOCKED)
> + lock_flag = 'l';
> seq_printf(m,
> "\n%5d 0x%pK-0x%pK %c%c%c%c%c%c 0x%08lx000",
> pt->pid,
> @@ -710,7 +716,7 @@ int drm_vma_info(struct seq_file *m, void *data)
> vma->vm_flags & VM_WRITE ? 'w' : '-',
> vma->vm_flags & VM_EXEC ? 'x' : '-',
> vma->vm_flags & VM_MAYSHARE ? 's' : 'p',
> - vma->vm_flags & VM_LOCKED ? 'l' : '-',
> + lock_flag,
> vma->vm_flags & VM_IO ? 'i' : '-',
> vma->vm_pgoff);
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ca1e091..38d69fc 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -579,6 +579,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)

This function has the following comment:

Don't forget to update Documentation/ on changes.

[...]

> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -92,7 +92,7 @@ retry:
> */
> mark_page_accessed(page);
> }
> - if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
> + if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
> /*
> * The preliminary mapping check is mainly to avoid the
> * pointless overhead of lock_page on the ZERO_PAGE
> @@ -265,6 +265,9 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
> unsigned int fault_flags = 0;
> int ret;
>
> + /* mlock all present pages, but do not fault in new pages */
> + if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
> + return -ENOENT;
> /* For mm_populate(), just skip the stack guard page. */
> if ((*flags & FOLL_POPULATE) &&
> (stack_guard_page_start(vma, address) ||
> @@ -850,7 +853,10 @@ long populate_vma_page_range(struct vm_area_struct *vma,
> VM_BUG_ON_VMA(end > vma->vm_end, vma);
> VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
>
> - gup_flags = FOLL_TOUCH | FOLL_POPULATE;
> + gup_flags = FOLL_TOUCH | FOLL_MLOCK;
> + if ((vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT)) == VM_LOCKED)
> + gup_flags |= FOLL_POPULATE;
> +
> /*
> * We want to touch writable mappings with a write fault in order
> * to break COW, except for shared mappings because these don't COW

I think this might be breaking the populate part of mmap(MAP_POPULATE &
~MAP_LOCKED) case, if I follow the execution correctly (it's far from
simple...)

SYSCALL_DEFINE6(mmap_pgoff... with MAP_POPULATE
vm_mmap_pgoff(..., MAP_POPULATE...)
do_mmap_pgoff(...MAP_POPULATE... &populate) -> populate == TRUE
mm_populate()
__mm_populate()
populate_vma_page_range()

Previously, this path would have FOLL_POPULATE in gup_flags and continue
with __get_user_pages() and faultin_page() (actually regardless of
FOLL_POPULATE) which would fault in the pages.

After your patch, populate_vma_page_range() will set FOLL_MLOCK, but
since VM_LOCKED is not set, FOLL_POPULATE won't be set either.
Then faultin_page() will return on the new check:

flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK

2015-08-06 15:53:37

by Kirill A. Shutemov

Subject: Re: [PATCH V6 3/6] mm: Introduce VM_LOCKONFAULT

On Thu, Aug 06, 2015 at 05:33:54PM +0200, Vlastimil Babka wrote:
> On 07/29/2015 05:42 PM, Eric B Munson wrote:
> >The cost of faulting in all memory to be locked can be very high when
> >working with large mappings. If only portions of the mapping will be
> >used this can incur a high penalty for locking.
> >
> >For the example of a large file, this is the usage pattern for a large
> >statical language model (probably applies to other statical or graphical
> >models as well). For the security example, any application transacting
> >in data that cannot be swapped out (credit card data, medical records,
> >etc).
> >
> >This patch introduces the ability to request that pages are not
> >pre-faulted, but are placed on the unevictable LRU when they are finally
> >faulted in. The VM_LOCKONFAULT flag will be used together with
> >VM_LOCKED and has no effect when set without VM_LOCKED. Setting the
> >VM_LOCKONFAULT flag for a VMA will cause pages faulted into that VMA to
> >be added to the unevictable LRU when they are faulted or if they are
> >already present, but will not cause any missing pages to be faulted in.
> >
> >Exposing this new lock state means that we cannot overload the meaning
> >of the FOLL_POPULATE flag any longer. Prior to this patch it was used
> >to mean that the VMA for a fault was locked. This means we need the
> >new FOLL_MLOCK flag to communicate the locked state of a VMA.
> >FOLL_POPULATE will now only control if the VMA should be populated and
> >in the case of VM_LOCKONFAULT, it will not be set.
> >
> >Signed-off-by: Eric B Munson <[email protected]>
> >Acked-by: Kirill A. Shutemov <[email protected]>
> >Cc: Michal Hocko <[email protected]>
> >Cc: Vlastimil Babka <[email protected]>
> >Cc: Jonathan Corbet <[email protected]>
> >Cc: "Kirill A. Shutemov" <[email protected]>
> >Cc: [email protected]
> >Cc: [email protected]
> >Cc: [email protected]
> >Cc: [email protected]
> >---
> > drivers/gpu/drm/drm_vm.c | 8 +++++++-
> > fs/proc/task_mmu.c | 1 +
> > include/linux/mm.h | 2 ++
> > kernel/fork.c | 2 +-
> > mm/debug.c | 1 +
> > mm/gup.c | 10 ++++++++--
> > mm/huge_memory.c | 2 +-
> > mm/hugetlb.c | 4 ++--
> > mm/mlock.c | 2 +-
> > mm/mmap.c | 2 +-
> > mm/rmap.c | 4 ++--
> > 11 files changed, 27 insertions(+), 11 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
> >index aab49ee..103a5f6 100644
> >--- a/drivers/gpu/drm/drm_vm.c
> >+++ b/drivers/gpu/drm/drm_vm.c
> >@@ -699,9 +699,15 @@ int drm_vma_info(struct seq_file *m, void *data)
> > (void *)(unsigned long)virt_to_phys(high_memory));
> >
> > list_for_each_entry(pt, &dev->vmalist, head) {
> >+ char lock_flag = '-';
> >+
> > vma = pt->vma;
> > if (!vma)
> > continue;
> >+ if (vma->vm_flags & VM_LOCKONFAULT)
> >+ lock_flag = 'f';
> >+ else if (vma->vm_flags & VM_LOCKED)
> >+ lock_flag = 'l';
> > seq_printf(m,
> > "\n%5d 0x%pK-0x%pK %c%c%c%c%c%c 0x%08lx000",
> > pt->pid,
> >@@ -710,7 +716,7 @@ int drm_vma_info(struct seq_file *m, void *data)
> > vma->vm_flags & VM_WRITE ? 'w' : '-',
> > vma->vm_flags & VM_EXEC ? 'x' : '-',
> > vma->vm_flags & VM_MAYSHARE ? 's' : 'p',
> >- vma->vm_flags & VM_LOCKED ? 'l' : '-',
> >+ lock_flag,
> > vma->vm_flags & VM_IO ? 'i' : '-',
> > vma->vm_pgoff);
> >
> >diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> >index ca1e091..38d69fc 100644
> >--- a/fs/proc/task_mmu.c
> >+++ b/fs/proc/task_mmu.c
> >@@ -579,6 +579,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>
> This function has the following comment:
>
> Don't forget to update Documentation/ on changes.
>
> [...]
>
> >--- a/mm/gup.c
> >+++ b/mm/gup.c
> >@@ -92,7 +92,7 @@ retry:
> > */
> > mark_page_accessed(page);
> > }
> >- if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
> >+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
> > /*
> > * The preliminary mapping check is mainly to avoid the
> > * pointless overhead of lock_page on the ZERO_PAGE
> >@@ -265,6 +265,9 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
> > unsigned int fault_flags = 0;
> > int ret;
> >
> >+ /* mlock all present pages, but do not fault in new pages */
> >+ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
> >+ return -ENOENT;
> > /* For mm_populate(), just skip the stack guard page. */
> > if ((*flags & FOLL_POPULATE) &&
> > (stack_guard_page_start(vma, address) ||
> >@@ -850,7 +853,10 @@ long populate_vma_page_range(struct vm_area_struct *vma,
> > VM_BUG_ON_VMA(end > vma->vm_end, vma);
> > VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
> >
> >- gup_flags = FOLL_TOUCH | FOLL_POPULATE;
> >+ gup_flags = FOLL_TOUCH | FOLL_MLOCK;
> >+ if ((vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT)) == VM_LOCKED)
> >+ gup_flags |= FOLL_POPULATE;
> >+
> > /*
> > * We want to touch writable mappings with a write fault in order
> > * to break COW, except for shared mappings because these don't COW
>
> I think this might be breaking the populate part of mmap(MAP_POPULATE &
> ~MAP_LOCKED) case, if I follow the execution correctly (it's far from
> simple...)
>
> SYSCALL_DEFINE6(mmap_pgoff... with MAP_POPULATE
> vm_mmap_pgoff(..., MAP_POPULATE...)
> do_mmap_pgoff(...MAP_POPULATE... &populate) -> populate == TRUE
> mm_populate()
> __mm_populate()
> populate_vma_page_range()
>
> Previously, this path would have FOLL_POPULATE in gup_flags and continue
> with __get_user_pages() and faultin_page() (actually regardless of
> FOLL_POPULATE) which would fault in the pages.
>
> After your patch, populate_vma_page_range() will set FOLL_MLOCK, but since
> VM_LOCKED is not set, FOLL_POPULATE won't be set either.
> Then faultin_page() will return on the new check:
>
> flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK

Good catch!

I guess it should be something like:

gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
if (vma->vm_flags & VM_LOCKONFAULT)
gup_flags &= ~FOLL_POPULATE;

--
Kirill A. Shutemov

2015-08-07 10:33:47

by Eric B Munson

Subject: Re: [PATCH V6 3/6] mm: Introduce VM_LOCKONFAULT

On Thu, 06 Aug 2015, Vlastimil Babka wrote:

...
> >
> >diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> >index ca1e091..38d69fc 100644
> >--- a/fs/proc/task_mmu.c
> >+++ b/fs/proc/task_mmu.c
> >@@ -579,6 +579,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>
> This function has the following comment:
>
> Don't forget to update Documentation/ on changes.
>
> [...]
>
> >--- a/mm/gup.c
> >+++ b/mm/gup.c
> >@@ -92,7 +92,7 @@ retry:
> > */
> > mark_page_accessed(page);
> > }
> >- if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
> >+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
> > /*
> > * The preliminary mapping check is mainly to avoid the
> > * pointless overhead of lock_page on the ZERO_PAGE
> >@@ -265,6 +265,9 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
> > unsigned int fault_flags = 0;
> > int ret;
> >
> >+ /* mlock all present pages, but do not fault in new pages */
> >+ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
> >+ return -ENOENT;
> > /* For mm_populate(), just skip the stack guard page. */
> > if ((*flags & FOLL_POPULATE) &&
> > (stack_guard_page_start(vma, address) ||
> >@@ -850,7 +853,10 @@ long populate_vma_page_range(struct vm_area_struct *vma,
> > VM_BUG_ON_VMA(end > vma->vm_end, vma);
> > VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
> >
> >- gup_flags = FOLL_TOUCH | FOLL_POPULATE;
> >+ gup_flags = FOLL_TOUCH | FOLL_MLOCK;
> >+ if ((vma->vm_flags & (VM_LOCKED | VM_LOCKONFAULT)) == VM_LOCKED)
> >+ gup_flags |= FOLL_POPULATE;
> >+
> > /*
> > * We want to touch writable mappings with a write fault in order
> > * to break COW, except for shared mappings because these don't COW
>
> I think this might be breaking the populate part of
> mmap(MAP_POPULATE & ~MAP_LOCKED) case, if I follow the execution
> correctly (it's far from simple...)
>
> SYSCALL_DEFINE6(mmap_pgoff... with MAP_POPULATE
> vm_mmap_pgoff(..., MAP_POPULATE...)
> do_mmap_pgoff(...MAP_POPULATE... &populate) -> populate == TRUE
> mm_populate()
> __mm_populate()
> populate_vma_page_range()
>
> Previously, this path would have FOLL_POPULATE in gup_flags and
> continue with __get_user_pages() and faultin_page() (actually
> regardless of FOLL_POPULATE) which would fault in the pages.
>
> After your patch, populate_vma_page_range() will set FOLL_MLOCK, but
> since VM_LOCKED is not set, FOLL_POPULATE won't be set either.
> Then faultin_page() will return on the new check:
>
> flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK
>
>

I am on vacation atm but I will try and get to respin this series after
making sure there aren't any more FOLL flag issues.

Thanks for keeping with these :)

Eric

Attachments:

2015-08-07 11:50:09

by Vlastimil Babka

Subject: Re: [PATCH V6 4/6] mm: mlock: Add mlock flags to enable VM_LOCKONFAULT usage

On 07/29/2015 05:42 PM, Eric B Munson wrote:
> The previous patch introduced a flag that specified pages in a VMA
> should be placed on the unevictable LRU, but they should not be made
> present when the area is created. This patch adds the ability to set
> this state via the new mlock system calls.
>
> We add MLOCK_ONFAULT for mlock2 and MCL_ONFAULT for mlockall.
> MLOCK_ONFAULT will set the VM_LOCKONFAULT modifier for VM_LOCKED.
> MCL_ONFAULT should be used as a modifier to the two other mlockall
> flags. When used with MCL_CURRENT, all current mappings will be marked
> with VM_LOCKED | VM_LOCKONFAULT. When used with MCL_FUTURE, the
> mm->def_flags will be marked with VM_LOCKED | VM_LOCKONFAULT. When used
> with both MCL_CURRENT and MCL_FUTURE, all current mappings and
> mm->def_flags will be marked with VM_LOCKED | VM_LOCKONFAULT.
>
> Prior to this patch, mlockall() will unconditionally clear the
> mm->def_flags any time it is called without MCL_FUTURE. This behavior
> is maintained after adding MCL_ONFAULT. If a call to
> mlockall(MCL_FUTURE) is followed by mlockall(MCL_CURRENT), the
> mm->def_flags will be cleared and new VMAs will be unlocked. This
> remains true with or without MCL_ONFAULT in either mlockall()
> invocation.
>
> munlock() will unconditionally clear both vma flags. munlockall()
> unconditionally clears for VMA flags on all VMAs and in the
> mm->def_flags field.
>
> Signed-off-by: Eric B Munson <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Vlastimil Babka <[email protected]>

The logic seems ok, although the fact that apply_mlockall_flags() is
shared by both mlockall and munlockall makes it even more subtle than
before :)

Anyway, just some nitpicks below.

Acked-by: Vlastimil Babka <[email protected]>

[...]

> +/*
> + * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
> + * and translate into the appropriate modifications to mm->def_flags and/or the
> + * flags for all current VMAs.
> + *
> + * There are a couple of sublties with this. If mlockall() is called multiple

^ typo

> + * times with different flags, the values do not necessarily stack. If mlockall
> + * is called once including the MCL_FUTURE flag and then a second time without
> + * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
> + */
> static int apply_mlockall_flags(int flags)
> {
> struct vm_area_struct * vma, * prev = NULL;
> + vm_flags_t to_add = 0;
>
> - if (flags & MCL_FUTURE)
> + current->mm->def_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
> + if (flags & MCL_FUTURE) {
> current->mm->def_flags |= VM_LOCKED;
> - else
> - current->mm->def_flags &= ~VM_LOCKED;
>
> - if (flags == MCL_FUTURE)
> - goto out;
> + if (flags & MCL_ONFAULT)
> + current->mm->def_flags |= VM_LOCKONFAULT;
> +
> + /*
> + * When there were only two flags, we used to early out if only
> + * MCL_FUTURE was set. Now that we have MCL_ONFAULT, we can
> + * only early out if MCL_FUTURE is set, but MCL_CURRENT is not.

Describing the relation to history of individual code lines in such
detail is noise imho. The stacking subtleties is already described above.

> + * This is done, even though it promotes odd behavior, to
> + * maintain behavior from older kernels
> + */
> + if (!(flags & MCL_CURRENT))
> + goto out;

2015-08-07 12:35:32

by Thierry Reding

Subject: Re: [PATCH V6 3/6] mm: Introduce VM_LOCKONFAULT

On Wed, Jul 29, 2015 at 11:42:52AM -0400, Eric B Munson wrote:
[...]
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ca1e091..38d69fc 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -579,6 +579,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> #ifdef CONFIG_X86_INTEL_MPX
> [ilog2(VM_MPX)] = "mp",
> #endif
> + [ilog2(VM_LOCKONFAULT)] = "lf",
> [ilog2(VM_LOCKED)] = "lo",
> [ilog2(VM_IO)] = "io",
> [ilog2(VM_SEQ_READ)] = "sr",
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 2e872f9..c2f3551 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -127,6 +127,7 @@ extern unsigned int kobjsize(const void *objp);
> #define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
> #define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
>
> +#define VM_LOCKONFAULT 0x00001000 /* Lock the pages covered when they are faulted in */
> #define VM_LOCKED 0x00002000
> #define VM_IO 0x00004000 /* Memory mapped I/O or similar */
>

This clashes with another change currently in linux-next:

81d056997385 userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP

Adding Andrea for visibility.

I noticed this because I was trying to make selftests/vm/mlock2-tests
work to see if the new mlock2 syscall would work on ARM. It didn't, so I
had to investigate and noticed that two symbolic names resolve to the
same value, which results in the mnemonics table (first hunk above)
overwriting the VM_LOCKONFAULT entry with the VM_UFFD_WP entry.

I've applied the following patch locally to fix this up.

Andrew, I think both of those patches came in via your tree, so perhaps
the best thing would be to squash the below (provided everybody agrees
that it's the right fix) into Eric's patch, adding the VM_LOCKONFAULT
flag?

Thierry

---- >8 ----
From a0003ebfeb15f91094d17961633cabb4e1beed21 Mon Sep 17 00:00:00 2001
From: Thierry Reding <[email protected]>
Date: Fri, 7 Aug 2015 14:23:42 +0200
Subject: [PATCH] mm: Fix VM_LOCKONFAULT clash with VM_UFFD_WP

Currently two patches in linux-next add new VM flags and unfortunately
two flags end up using the same value. This results for example in the
/proc/pid/smaps file not listing the VM_LOCKONFAULT flag, which breaks
tools/testing/selftests/vm/mlock2-tests.

Signed-off-by: Thierry Reding <[email protected]>
---
fs/proc/task_mmu.c | 2 +-
include/linux/mm.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index bdd7e48a85f0..893e4b9bb2da 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -592,13 +592,13 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
#ifdef CONFIG_X86_INTEL_MPX
[ilog2(VM_MPX)] = "mp",
#endif
- [ilog2(VM_LOCKONFAULT)] = "lf",
[ilog2(VM_LOCKED)] = "lo",
[ilog2(VM_IO)] = "io",
[ilog2(VM_SEQ_READ)] = "sr",
[ilog2(VM_RAND_READ)] = "rr",
[ilog2(VM_DONTCOPY)] = "dc",
[ilog2(VM_DONTEXPAND)] = "de",
+ [ilog2(VM_LOCKONFAULT)] = "lf",
[ilog2(VM_ACCOUNT)] = "ac",
[ilog2(VM_NORESERVE)] = "nr",
[ilog2(VM_HUGETLB)] = "ht",
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 363ea2cda35f..cb4e1737d669 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -129,7 +129,6 @@ extern unsigned int kobjsize(const void *objp);
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
#define VM_UFFD_WP 0x00001000 /* wrprotect pages tracking */

-#define VM_LOCKONFAULT 0x00001000 /* Lock the pages covered when they are faulted in */
#define VM_LOCKED 0x00002000
#define VM_IO 0x00004000 /* Memory mapped I/O or similar */

@@ -139,6 +138,7 @@ extern unsigned int kobjsize(const void *objp);

#define VM_DONTCOPY 0x00020000 /* Do not copy this vma on fork */
#define VM_DONTEXPAND 0x00040000 /* Cannot expand with mremap() */
+#define VM_LOCKONFAULT 0x00080000 /* Lock the pages covered when they are faulted in */
#define VM_ACCOUNT 0x00100000 /* Is a VM accounted object */
#define VM_NORESERVE 0x00200000 /* should the VM suppress accounting */
#define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
--
2.4.5

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