Changes since v5 [1]:
1) Merged with Dan's changes to fs/dax.c that were staged in -mm and -next.
2) Store sectors in the address_space radix tree for DAX entries instead of
addresses. This allows us to get the addresses from the block driver
via dax_map_atomic() during fsync/msync so that we can protect against
races with block device removal. (Dan)
3) Reordered things a bit in dax_writeback_one() so we clear the
PAGECACHE_TAG_TOWRITE tag even if the radix tree entry is corrupt. This
prevents us from getting into an infinite loop where we don't proceed far
enough in dax_writeback_one() to clear that flag, but
dax_writeback_mapping_range() will keep finding that entry via
find_get_entries_tag().
4) Changed the ordering of the radix tree insertion so that it happens
before the page insertion into the page tables. This ensures that we don't
end up in a case where the page table insertion succeeds and the radix tree
insertion fails which could give us a writeable PTE that has no
corresponding radix tree entry.
5) Got rid of the 'nrdax' variable in struct address_space and renamed
'nrshadows' to 'nrexceptional' so that it can be used for both DAX and
shadow exceptional entries. We explicitly prevent shadow entries from
being added to radix trees for DAX mappings, so the single counter can
safely be reused for both purposes. (Jan)
6) Updated all my WARN_ON() calls so I use the return value to know whether
I've hit an erorr. (Andrew)
This series applies cleanly and was tested against next-20151223.
A working tree can be found here:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=fsync_v6
[1]: https://lists.01.org/pipermail/linux-nvdimm/2015-December/003588.html
Ross Zwisler (7):
pmem: add wb_cache_pmem() to the PMEM API
dax: support dirty DAX entries in radix tree
mm: add find_get_entries_tag()
dax: add support for fsync/msync
ext2: call dax_pfn_mkwrite() for DAX fsync/msync
ext4: call dax_pfn_mkwrite() for DAX fsync/msync
xfs: call dax_pfn_mkwrite() for DAX fsync/msync
arch/x86/include/asm/pmem.h | 11 +--
fs/block_dev.c | 2 +-
fs/dax.c | 196 ++++++++++++++++++++++++++++++++++++++++++--
fs/ext2/file.c | 4 +-
fs/ext4/file.c | 4 +-
fs/inode.c | 2 +-
fs/xfs/xfs_file.c | 7 +-
include/linux/dax.h | 7 ++
include/linux/fs.h | 3 +-
include/linux/pagemap.h | 3 +
include/linux/pmem.h | 22 ++++-
include/linux/radix-tree.h | 9 ++
mm/filemap.c | 91 ++++++++++++++++++--
mm/truncate.c | 69 +++++++++-------
mm/vmscan.c | 9 +-
mm/workingset.c | 4 +-
16 files changed, 384 insertions(+), 59 deletions(-)
--
2.6.3
The function __arch_wb_cache_pmem() was already an internal implementation
detail of the x86 PMEM API, but this functionality needs to be exported as
part of the general PMEM API to handle the fsync/msync case for DAX mmaps.
One thing worth noting is that we really do want this to be part of the
PMEM API as opposed to a stand-alone function like clflush_cache_range()
because of ordering restrictions. By having wb_cache_pmem() as part of the
PMEM API we can leave it unordered, call it multiple times to write back
large amounts of memory, and then order the multiple calls with a single
wmb_pmem().
Signed-off-by: Ross Zwisler <[email protected]>
---
arch/x86/include/asm/pmem.h | 11 ++++++-----
include/linux/pmem.h | 22 +++++++++++++++++++++-
2 files changed, 27 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index 1544fab..c57fd1e 100644
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -67,18 +67,19 @@ static inline void arch_wmb_pmem(void)
}
/**
- * __arch_wb_cache_pmem - write back a cache range with CLWB
+ * arch_wb_cache_pmem - write back a cache range with CLWB
* @vaddr: virtual start address
* @size: number of bytes to write back
*
* Write back a cache range using the CLWB (cache line write back)
* instruction. This function requires explicit ordering with an
- * arch_wmb_pmem() call. This API is internal to the x86 PMEM implementation.
+ * arch_wmb_pmem() call.
*/
-static inline void __arch_wb_cache_pmem(void *vaddr, size_t size)
+static inline void arch_wb_cache_pmem(void __pmem *addr, size_t size)
{
u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
unsigned long clflush_mask = x86_clflush_size - 1;
+ void *vaddr = (void __force *)addr;
void *vend = vaddr + size;
void *p;
@@ -115,7 +116,7 @@ static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
len = copy_from_iter_nocache(vaddr, bytes, i);
if (__iter_needs_pmem_wb(i))
- __arch_wb_cache_pmem(vaddr, bytes);
+ arch_wb_cache_pmem(addr, bytes);
return len;
}
@@ -133,7 +134,7 @@ static inline void arch_clear_pmem(void __pmem *addr, size_t size)
void *vaddr = (void __force *)addr;
memset(vaddr, 0, size);
- __arch_wb_cache_pmem(vaddr, size);
+ arch_wb_cache_pmem(addr, size);
}
static inline bool __arch_has_wmb_pmem(void)
diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index acfea8c..7c3d11a 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -53,12 +53,18 @@ static inline void arch_clear_pmem(void __pmem *addr, size_t size)
{
BUG();
}
+
+static inline void arch_wb_cache_pmem(void __pmem *addr, size_t size)
+{
+ BUG();
+}
#endif
/*
* Architectures that define ARCH_HAS_PMEM_API must provide
* implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(),
- * arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
+ * arch_copy_from_iter_pmem(), arch_clear_pmem(), arch_wb_cache_pmem()
+ * and arch_has_wmb_pmem().
*/
static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
{
@@ -178,4 +184,18 @@ static inline void clear_pmem(void __pmem *addr, size_t size)
else
default_clear_pmem(addr, size);
}
+
+/**
+ * wb_cache_pmem - write back processor cache for PMEM memory range
+ * @addr: virtual start address
+ * @size: number of bytes to write back
+ *
+ * Write back the processor cache range starting at 'addr' for 'size' bytes.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline void wb_cache_pmem(void __pmem *addr, size_t size)
+{
+ if (arch_has_pmem_api())
+ arch_wb_cache_pmem(addr, size);
+}
#endif /* __PMEM_H__ */
--
2.6.3
Add support for tracking dirty DAX entries in the struct address_space
radix tree. This tree is already used for dirty page writeback, and it
already supports the use of exceptional (non struct page*) entries.
In order to properly track dirty DAX pages we will insert new exceptional
entries into the radix tree that represent dirty DAX PTE or PMD pages.
These exceptional entries will also contain the writeback sectors for the
PTE or PMD faults that we can use at fsync/msync time.
There are currently two types of exceptional entries (shmem and shadow)
that can be placed into the radix tree, and this adds a third. We rely on
the fact that only one type of exceptional entry can be found in a given
radix tree based on its usage. This happens for free with DAX vs shmem but
we explicitly prevent shadow entries from being added to radix trees for
DAX mappings.
The only shadow entries that would be generated for DAX radix trees would
be to track zero page mappings that were created for holes. These pages
would receive minimal benefit from having shadow entries, and the choice
to have only one type of exceptional entry in a given radix tree makes the
logic simpler both in clear_exceptional_entry() and in the rest of DAX.
Signed-off-by: Ross Zwisler <[email protected]>
---
fs/block_dev.c | 2 +-
fs/inode.c | 2 +-
include/linux/dax.h | 5 ++++
include/linux/fs.h | 3 +-
include/linux/radix-tree.h | 9 ++++++
mm/filemap.c | 17 ++++++++----
mm/truncate.c | 69 ++++++++++++++++++++++++++--------------------
mm/vmscan.c | 9 +++++-
mm/workingset.c | 4 +--
9 files changed, 78 insertions(+), 42 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 8c1f467..29b9c9b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -75,7 +75,7 @@ void kill_bdev(struct block_device *bdev)
{
struct address_space *mapping = bdev->bd_inode->i_mapping;
- if (mapping->nrpages == 0 && mapping->nrshadows == 0)
+ if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
return;
invalidate_bh_lrus();
diff --git a/fs/inode.c b/fs/inode.c
index 4c8f719..6e3e5d0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -495,7 +495,7 @@ void clear_inode(struct inode *inode)
*/
spin_lock_irq(&inode->i_data.tree_lock);
BUG_ON(inode->i_data.nrpages);
- BUG_ON(inode->i_data.nrshadows);
+ BUG_ON(inode->i_data.nrexceptional);
spin_unlock_irq(&inode->i_data.tree_lock);
BUG_ON(!list_empty(&inode->i_data.private_list));
BUG_ON(!(inode->i_state & I_FREEING));
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b415e52..e9d57f68 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -36,4 +36,9 @@ static inline bool vma_is_dax(struct vm_area_struct *vma)
{
return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
}
+
+static inline bool dax_mapping(struct address_space *mapping)
+{
+ return mapping->host && IS_DAX(mapping->host);
+}
#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 12ba937..905565f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -432,7 +432,8 @@ struct address_space {
struct rw_semaphore i_mmap_rwsem; /* protect tree, count, list */
/* Protected by tree_lock together with the radix tree */
unsigned long nrpages; /* number of total pages */
- unsigned long nrshadows; /* number of shadow entries */
+ /* number of shadow or DAX exceptional entries */
+ unsigned long nrexceptional;
pgoff_t writeback_index;/* writeback starts here */
const struct address_space_operations *a_ops; /* methods */
unsigned long flags; /* error bits/gfp mask */
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 33170db..ba8e0fc 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -51,6 +51,15 @@
#define RADIX_TREE_EXCEPTIONAL_ENTRY 2
#define RADIX_TREE_EXCEPTIONAL_SHIFT 2
+#define RADIX_DAX_MASK 0xf
+#define RADIX_DAX_SHIFT 4
+#define RADIX_DAX_PTE (0x4 | RADIX_TREE_EXCEPTIONAL_ENTRY)
+#define RADIX_DAX_PMD (0x8 | RADIX_TREE_EXCEPTIONAL_ENTRY)
+#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK)
+#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
+#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
+ RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE)))
+
static inline int radix_tree_is_indirect_ptr(void *ptr)
{
return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
diff --git a/mm/filemap.c b/mm/filemap.c
index 847ee43..7b8be78 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -11,6 +11,7 @@
*/
#include <linux/export.h>
#include <linux/compiler.h>
+#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/capability.h>
@@ -123,9 +124,9 @@ static void page_cache_tree_delete(struct address_space *mapping,
__radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
if (shadow) {
- mapping->nrshadows++;
+ mapping->nrexceptional++;
/*
- * Make sure the nrshadows update is committed before
+ * Make sure the nrexceptional update is committed before
* the nrpages update so that final truncate racing
* with reclaim does not see both counters 0 at the
* same time and miss a shadow entry.
@@ -579,9 +580,13 @@ static int page_cache_tree_insert(struct address_space *mapping,
p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
if (!radix_tree_exceptional_entry(p))
return -EEXIST;
+
+ if (WARN_ON(dax_mapping(mapping)))
+ return -EINVAL;
+
if (shadowp)
*shadowp = p;
- mapping->nrshadows--;
+ mapping->nrexceptional--;
if (node)
workingset_node_shadows_dec(node);
}
@@ -1245,9 +1250,9 @@ repeat:
if (radix_tree_deref_retry(page))
goto restart;
/*
- * A shadow entry of a recently evicted page,
- * or a swap entry from shmem/tmpfs. Return
- * it without attempting to raise page count.
+ * A shadow entry of a recently evicted page, a swap
+ * entry from shmem/tmpfs or a DAX entry. Return it
+ * without attempting to raise page count.
*/
goto export;
}
diff --git a/mm/truncate.c b/mm/truncate.c
index 76e35ad..e3ee0e2 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -9,6 +9,7 @@
#include <linux/kernel.h>
#include <linux/backing-dev.h>
+#include <linux/dax.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
@@ -34,31 +35,39 @@ static void clear_exceptional_entry(struct address_space *mapping,
return;
spin_lock_irq(&mapping->tree_lock);
- /*
- * Regular page slots are stabilized by the page lock even
- * without the tree itself locked. These unlocked entries
- * need verification under the tree lock.
- */
- if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot))
- goto unlock;
- if (*slot != entry)
- goto unlock;
- radix_tree_replace_slot(slot, NULL);
- mapping->nrshadows--;
- if (!node)
- goto unlock;
- workingset_node_shadows_dec(node);
- /*
- * Don't track node without shadow entries.
- *
- * Avoid acquiring the list_lru lock if already untracked.
- * The list_empty() test is safe as node->private_list is
- * protected by mapping->tree_lock.
- */
- if (!workingset_node_shadows(node) &&
- !list_empty(&node->private_list))
- list_lru_del(&workingset_shadow_nodes, &node->private_list);
- __radix_tree_delete_node(&mapping->page_tree, node);
+
+ if (dax_mapping(mapping)) {
+ if (radix_tree_delete_item(&mapping->page_tree, index, entry))
+ mapping->nrexceptional--;
+ } else {
+ /*
+ * Regular page slots are stabilized by the page lock even
+ * without the tree itself locked. These unlocked entries
+ * need verification under the tree lock.
+ */
+ if (!__radix_tree_lookup(&mapping->page_tree, index, &node,
+ &slot))
+ goto unlock;
+ if (*slot != entry)
+ goto unlock;
+ radix_tree_replace_slot(slot, NULL);
+ mapping->nrexceptional--;
+ if (!node)
+ goto unlock;
+ workingset_node_shadows_dec(node);
+ /*
+ * Don't track node without shadow entries.
+ *
+ * Avoid acquiring the list_lru lock if already untracked.
+ * The list_empty() test is safe as node->private_list is
+ * protected by mapping->tree_lock.
+ */
+ if (!workingset_node_shadows(node) &&
+ !list_empty(&node->private_list))
+ list_lru_del(&workingset_shadow_nodes,
+ &node->private_list);
+ __radix_tree_delete_node(&mapping->page_tree, node);
+ }
unlock:
spin_unlock_irq(&mapping->tree_lock);
}
@@ -228,7 +237,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
int i;
cleancache_invalidate_inode(mapping);
- if (mapping->nrpages == 0 && mapping->nrshadows == 0)
+ if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
return;
/* Offsets within partial pages */
@@ -402,7 +411,7 @@ EXPORT_SYMBOL(truncate_inode_pages);
*/
void truncate_inode_pages_final(struct address_space *mapping)
{
- unsigned long nrshadows;
+ unsigned long nrexceptional;
unsigned long nrpages;
/*
@@ -416,14 +425,14 @@ void truncate_inode_pages_final(struct address_space *mapping)
/*
* When reclaim installs eviction entries, it increases
- * nrshadows first, then decreases nrpages. Make sure we see
+ * nrexceptional first, then decreases nrpages. Make sure we see
* this in the right order or we might miss an entry.
*/
nrpages = mapping->nrpages;
smp_rmb();
- nrshadows = mapping->nrshadows;
+ nrexceptional = mapping->nrexceptional;
- if (nrpages || nrshadows) {
+ if (nrpages || nrexceptional) {
/*
* As truncation uses a lockless tree lookup, cycle
* the tree lock to make sure any ongoing tree
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 44ec50f..30e0cd7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -46,6 +46,7 @@
#include <linux/oom.h>
#include <linux/prefetch.h>
#include <linux/printk.h>
+#include <linux/dax.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -671,9 +672,15 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
* inode reclaim needs to empty out the radix tree or
* the nodes are lost. Don't plant shadows behind its
* back.
+ *
+ * We also don't store shadows for DAX mappings because the
+ * only page cache pages found in these are zero pages
+ * covering holes, and because we don't want to mix DAX
+ * exceptional entries and shadow exceptional entries in the
+ * same page_tree.
*/
if (reclaimed && page_is_file_cache(page) &&
- !mapping_exiting(mapping))
+ !mapping_exiting(mapping) && !dax_mapping(mapping))
shadow = workingset_eviction(mapping, page);
__delete_from_page_cache(page, shadow, memcg);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
diff --git a/mm/workingset.c b/mm/workingset.c
index aa01713..61ead9e 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -351,8 +351,8 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
node->slots[i] = NULL;
BUG_ON(node->count < (1U << RADIX_TREE_COUNT_SHIFT));
node->count -= 1U << RADIX_TREE_COUNT_SHIFT;
- BUG_ON(!mapping->nrshadows);
- mapping->nrshadows--;
+ BUG_ON(!mapping->nrexceptional);
+ mapping->nrexceptional--;
}
}
BUG_ON(node->count);
--
2.6.3
Add find_get_entries_tag() to the family of functions that include
find_get_entries(), find_get_pages() and find_get_pages_tag(). This is
needed for DAX dirty page handling because we need a list of both page
offsets and radix tree entries ('indices' and 'entries' in this function)
that are marked with the PAGECACHE_TAG_TOWRITE tag.
Signed-off-by: Ross Zwisler <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
---
include/linux/pagemap.h | 3 +++
mm/filemap.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 4d08b6c..92395a0 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -361,6 +361,9 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
unsigned int nr_pages, struct page **pages);
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
int tag, unsigned int nr_pages, struct page **pages);
+unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
+ int tag, unsigned int nr_entries,
+ struct page **entries, pgoff_t *indices);
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags);
diff --git a/mm/filemap.c b/mm/filemap.c
index 7b8be78..1e215fc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1499,6 +1499,74 @@ repeat:
}
EXPORT_SYMBOL(find_get_pages_tag);
+/**
+ * find_get_entries_tag - find and return entries that match @tag
+ * @mapping: the address_space to search
+ * @start: the starting page cache index
+ * @tag: the tag index
+ * @nr_entries: the maximum number of entries
+ * @entries: where the resulting entries are placed
+ * @indices: the cache indices corresponding to the entries in @entries
+ *
+ * Like find_get_entries, except we only return entries which are tagged with
+ * @tag.
+ */
+unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
+ int tag, unsigned int nr_entries,
+ struct page **entries, pgoff_t *indices)
+{
+ void **slot;
+ unsigned int ret = 0;
+ struct radix_tree_iter iter;
+
+ if (!nr_entries)
+ return 0;
+
+ rcu_read_lock();
+restart:
+ radix_tree_for_each_tagged(slot, &mapping->page_tree,
+ &iter, start, tag) {
+ struct page *page;
+repeat:
+ page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ continue;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_deref_retry(page)) {
+ /*
+ * Transient condition which can only trigger
+ * when entry at index 0 moves out of or back
+ * to root: none yet gotten, safe to restart.
+ */
+ goto restart;
+ }
+
+ /*
+ * A shadow entry of a recently evicted page, a swap
+ * entry from shmem/tmpfs or a DAX entry. Return it
+ * without attempting to raise page count.
+ */
+ goto export;
+ }
+ if (!page_cache_get_speculative(page))
+ goto repeat;
+
+ /* Has the page moved? */
+ if (unlikely(page != *slot)) {
+ page_cache_release(page);
+ goto repeat;
+ }
+export:
+ indices[ret] = iter.index;
+ entries[ret] = page;
+ if (++ret == nr_entries)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(find_get_entries_tag);
+
/*
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
* a _large_ part of the i/o request. Imagine the worst scenario:
--
2.6.3
To properly handle fsync/msync in an efficient way DAX needs to track dirty
pages so it is able to flush them durably to media on demand.
The tracking of dirty pages is done via the radix tree in struct
address_space. This radix tree is already used by the page writeback
infrastructure for tracking dirty pages associated with an open file, and
it already has support for exceptional (non struct page*) entries. We
build upon these features to add exceptional entries to the radix tree for
DAX dirty PMD or PTE pages at fault time.
Signed-off-by: Ross Zwisler <[email protected]>
---
fs/dax.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++++++--
include/linux/dax.h | 2 +
mm/filemap.c | 6 ++
3 files changed, 198 insertions(+), 6 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 82d0bff..050610d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -24,6 +24,7 @@
#include <linux/memcontrol.h>
#include <linux/mm.h>
#include <linux/mutex.h>
+#include <linux/pagevec.h>
#include <linux/pmem.h>
#include <linux/sched.h>
#include <linux/uio.h>
@@ -323,6 +324,176 @@ static int copy_user_bh(struct page *to, struct inode *inode,
return 0;
}
+#define NO_SECTOR -1
+
+static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
+ sector_t sector, bool pmd_entry, bool dirty)
+{
+ struct radix_tree_root *page_tree = &mapping->page_tree;
+ int error = 0;
+ void *entry;
+
+ __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+
+ spin_lock_irq(&mapping->tree_lock);
+ entry = radix_tree_lookup(page_tree, index);
+
+ if (entry) {
+ if (!pmd_entry || RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+ goto dirty;
+ radix_tree_delete(&mapping->page_tree, index);
+ mapping->nrexceptional--;
+ }
+
+ if (sector == NO_SECTOR) {
+ /*
+ * This can happen during correct operation if our pfn_mkwrite
+ * fault raced against a hole punch operation. If this
+ * happens the pte that was hole punched will have been
+ * unmapped and the radix tree entry will have been removed by
+ * the time we are called, but the call will still happen. We
+ * will return all the way up to wp_pfn_shared(), where the
+ * pte_same() check will fail, eventually causing page fault
+ * to be retried by the CPU.
+ */
+ goto unlock;
+ }
+
+ error = radix_tree_insert(page_tree, index,
+ RADIX_DAX_ENTRY(sector, pmd_entry));
+ if (error)
+ goto unlock;
+
+ mapping->nrexceptional++;
+ dirty:
+ if (dirty)
+ radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
+ unlock:
+ spin_unlock_irq(&mapping->tree_lock);
+ return error;
+}
+
+static int dax_writeback_one(struct block_device *bdev,
+ struct address_space *mapping, pgoff_t index, void *entry)
+{
+ struct radix_tree_root *page_tree = &mapping->page_tree;
+ int type = RADIX_DAX_TYPE(entry);
+ struct radix_tree_node *node;
+ struct blk_dax_ctl dax;
+ void **slot;
+ int ret = 0;
+
+ spin_lock_irq(&mapping->tree_lock);
+ /*
+ * Regular page slots are stabilized by the page lock even
+ * without the tree itself locked. These unlocked entries
+ * need verification under the tree lock.
+ */
+ if (!__radix_tree_lookup(page_tree, index, &node, &slot))
+ goto unlock;
+ if (*slot != entry)
+ goto unlock;
+
+ /* another fsync thread may have already written back this entry */
+ if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
+ goto unlock;
+
+ radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
+
+ if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+ ret = -EIO;
+ goto unlock;
+ }
+
+ dax.sector = RADIX_DAX_SECTOR(entry);
+ dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+ spin_unlock_irq(&mapping->tree_lock);
+
+ /*
+ * We cannot hold tree_lock while calling dax_map_atomic() because it
+ * eventually calls cond_resched().
+ */
+ ret = dax_map_atomic(bdev, &dax);
+ if (ret < 0)
+ return ret;
+
+ if (WARN_ON_ONCE(ret < dax.size)) {
+ ret = -EIO;
+ dax_unmap_atomic(bdev, &dax);
+ return ret;
+ }
+
+ spin_lock_irq(&mapping->tree_lock);
+ /*
+ * We need to revalidate our radix entry while holding tree_lock
+ * before we do the writeback.
+ */
+ if (!__radix_tree_lookup(page_tree, index, &node, &slot))
+ goto unmap;
+ if (*slot != entry)
+ goto unmap;
+
+ wb_cache_pmem(dax.addr, dax.size);
+ unmap:
+ dax_unmap_atomic(bdev, &dax);
+ unlock:
+ spin_unlock_irq(&mapping->tree_lock);
+ return ret;
+}
+
+/*
+ * Flush the mapping to the persistent domain within the byte range of [start,
+ * end]. This is required by data integrity operations to ensure file data is
+ * on persistent storage prior to completion of the operation.
+ */
+int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
+ loff_t end)
+{
+ struct inode *inode = mapping->host;
+ struct block_device *bdev = inode->i_sb->s_bdev;
+ pgoff_t indices[PAGEVEC_SIZE];
+ pgoff_t start_page, end_page;
+ struct pagevec pvec;
+ void *entry;
+ int i, ret = 0;
+
+ if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
+ return -EIO;
+
+ rcu_read_lock();
+ entry = radix_tree_lookup(&mapping->page_tree, start & PMD_MASK);
+ rcu_read_unlock();
+
+ /* see if the start of our range is covered by a PMD entry */
+ if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+ start &= PMD_MASK;
+
+ start_page = start >> PAGE_CACHE_SHIFT;
+ end_page = end >> PAGE_CACHE_SHIFT;
+
+ tag_pages_for_writeback(mapping, start_page, end_page);
+
+ pagevec_init(&pvec, 0);
+ while (1) {
+ pvec.nr = find_get_entries_tag(mapping, start_page,
+ PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
+ pvec.pages, indices);
+
+ if (pvec.nr == 0)
+ break;
+
+ for (i = 0; i < pvec.nr; i++) {
+ ret = dax_writeback_one(bdev, mapping, indices[i],
+ pvec.pages[i]);
+ if (ret < 0)
+ return ret;
+ }
+ }
+ wmb_pmem();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
+
static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
@@ -362,6 +533,11 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
}
dax_unmap_atomic(bdev, &dax);
+ error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
+ vmf->flags & FAULT_FLAG_WRITE);
+ if (error)
+ goto out;
+
error = vm_insert_mixed(vma, vaddr, dax.pfn);
out:
@@ -486,6 +662,7 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
delete_from_page_cache(page);
unlock_page(page);
page_cache_release(page);
+ page = NULL;
}
/*
@@ -579,7 +756,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
struct block_device *bdev = NULL;
pgoff_t size, pgoff;
sector_t block;
- int result = 0;
+ int error, result = 0;
/* dax pmd mappings require pfn_t_devmap() */
if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
@@ -721,6 +898,16 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
}
dax_unmap_atomic(bdev, &dax);
+ if (write) {
+ error = dax_radix_entry(mapping, pgoff, dax.sector,
+ true, true);
+ if (error) {
+ dax_pmd_dbg(bdev, address,
+ "PMD radix insertion failed");
+ goto fallback;
+ }
+ }
+
dev_dbg(part_to_dev(bdev->bd_part),
"%s: %s addr: %lx pfn: %lx sect: %llx\n",
__func__, current->comm, address,
@@ -779,15 +966,12 @@ EXPORT_SYMBOL_GPL(dax_pmd_fault);
* dax_pfn_mkwrite - handle first write to DAX page
* @vma: The virtual memory area where the fault occurred
* @vmf: The description of the fault
- *
*/
int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
- struct super_block *sb = file_inode(vma->vm_file)->i_sb;
+ struct file *file = vma->vm_file;
- sb_start_pagefault(sb);
- file_update_time(vma->vm_file);
- sb_end_pagefault(sb);
+ dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false, true);
return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e9d57f68..8204c3d 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -41,4 +41,6 @@ static inline bool dax_mapping(struct address_space *mapping)
{
return mapping->host && IS_DAX(mapping->host);
}
+int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
+ loff_t end);
#endif
diff --git a/mm/filemap.c b/mm/filemap.c
index 1e215fc..2e7c8d9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -482,6 +482,12 @@ int filemap_write_and_wait_range(struct address_space *mapping,
{
int err = 0;
+ if (dax_mapping(mapping) && mapping->nrexceptional) {
+ err = dax_writeback_mapping_range(mapping, lstart, lend);
+ if (err)
+ return err;
+ }
+
if (mapping->nrpages) {
err = __filemap_fdatawrite_range(mapping, lstart, lend,
WB_SYNC_ALL);
--
2.6.3
To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can track when user pages are
dirtied.
Signed-off-by: Ross Zwisler <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
---
fs/ext2/file.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 11a42c5..2c88d68 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -102,8 +102,8 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
{
struct inode *inode = file_inode(vma->vm_file);
struct ext2_inode_info *ei = EXT2_I(inode);
- int ret = VM_FAULT_NOPAGE;
loff_t size;
+ int ret;
sb_start_pagefault(inode->i_sb);
file_update_time(vma->vm_file);
@@ -113,6 +113,8 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (vmf->pgoff >= size)
ret = VM_FAULT_SIGBUS;
+ else
+ ret = dax_pfn_mkwrite(vma, vmf);
up_read(&ei->dax_sem);
sb_end_pagefault(inode->i_sb);
--
2.6.3
To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can track when user pages are
dirtied.
Signed-off-by: Ross Zwisler <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
---
fs/ext4/file.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 60683ab..fa899c9 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -291,8 +291,8 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
{
struct inode *inode = file_inode(vma->vm_file);
struct super_block *sb = inode->i_sb;
- int ret = VM_FAULT_NOPAGE;
loff_t size;
+ int ret;
sb_start_pagefault(sb);
file_update_time(vma->vm_file);
@@ -300,6 +300,8 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (vmf->pgoff >= size)
ret = VM_FAULT_SIGBUS;
+ else
+ ret = dax_pfn_mkwrite(vma, vmf);
up_read(&EXT4_I(inode)->i_mmap_sem);
sb_end_pagefault(sb);
--
2.6.3
To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can track when user pages are
dirtied.
Signed-off-by: Ross Zwisler <[email protected]>
---
fs/xfs/xfs_file.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index f5392ab..40ffbb1 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1603,9 +1603,8 @@ xfs_filemap_pmd_fault(
/*
* pfn_mkwrite was originally inteneded to ensure we capture time stamp
* updates on write faults. In reality, it's need to serialise against
- * truncate similar to page_mkwrite. Hence we open-code dax_pfn_mkwrite()
- * here and cycle the XFS_MMAPLOCK_SHARED to ensure we serialise the fault
- * barrier in place.
+ * truncate similar to page_mkwrite. Hence we cycle the XFS_MMAPLOCK_SHARED
+ * to ensure we serialise the fault barrier in place.
*/
static int
xfs_filemap_pfn_mkwrite(
@@ -1628,6 +1627,8 @@ xfs_filemap_pfn_mkwrite(
size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (vmf->pgoff >= size)
ret = VM_FAULT_SIGBUS;
+ else if (IS_DAX(inode))
+ ret = dax_pfn_mkwrite(vma, vmf);
xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
sb_end_pagefault(inode->i_sb);
return ret;
--
2.6.3
> -----Original Message-----
> From: Linux-nvdimm [mailto:[email protected]] On Behalf Of
> Ross Zwisler
> Sent: Wednesday, December 23, 2015 1:39 PM
> Subject: [PATCH v6 3/7] mm: add find_get_entries_tag()
>
...
> diff --git a/mm/filemap.c b/mm/filemap.c
...
> +unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
> + int tag, unsigned int nr_entries,
> + struct page **entries, pgoff_t *indices)
> +{
> + void **slot;
> + unsigned int ret = 0;
...
> + radix_tree_for_each_tagged(slot, &mapping->page_tree,
> + &iter, start, tag) {
...
> + indices[ret] = iter.index;
> + entries[ret] = page;
> + if (++ret == nr_entries)
> + break;
> + }
Using >= would provide more safety from buffer overflow
problems in case ret ever jumped ahead by more than one.
---
Robert Elliott, HPE Persistent Memory
Hi Ross,
On 12/24/2015 03:39 AM, Ross Zwisler wrote:
> Add support for tracking dirty DAX entries in the struct address_space
> radix tree. This tree is already used for dirty page writeback, and it
> already supports the use of exceptional (non struct page*) entries.
>
> In order to properly track dirty DAX pages we will insert new exceptional
> entries into the radix tree that represent dirty DAX PTE or PMD pages.
I may get it wrong, but there is "struct page" for persistent memory after
"[PATCH v4 00/18]get_user_pages() for dax pte and pmd mappings".
So why not just add "struct page" to radix tree directly just like normal page cache?
Then we don't need to deal with any exceptional entries and special writeback.
Thanks,
Bob
> These exceptional entries will also contain the writeback sectors for the
> PTE or PMD faults that we can use at fsync/msync time.
>
> There are currently two types of exceptional entries (shmem and shadow)
> that can be placed into the radix tree, and this adds a third. We rely on
> the fact that only one type of exceptional entry can be found in a given
> radix tree based on its usage. This happens for free with DAX vs shmem but
> we explicitly prevent shadow entries from being added to radix trees for
> DAX mappings.
>
> The only shadow entries that would be generated for DAX radix trees would
> be to track zero page mappings that were created for holes. These pages
> would receive minimal benefit from having shadow entries, and the choice
> to have only one type of exceptional entry in a given radix tree makes the
> logic simpler both in clear_exceptional_entry() and in the rest of DAX.
>
> Signed-off-by: Ross Zwisler <[email protected]>
> ---
> fs/block_dev.c | 2 +-
> fs/inode.c | 2 +-
> include/linux/dax.h | 5 ++++
> include/linux/fs.h | 3 +-
> include/linux/radix-tree.h | 9 ++++++
> mm/filemap.c | 17 ++++++++----
> mm/truncate.c | 69 ++++++++++++++++++++++++++--------------------
> mm/vmscan.c | 9 +++++-
> mm/workingset.c | 4 +--
> 9 files changed, 78 insertions(+), 42 deletions(-)
On Wed, Dec 30, 2015 at 12:02 AM, Bob Liu <[email protected]> wrote:
> Hi Ross,
>
> On 12/24/2015 03:39 AM, Ross Zwisler wrote:
>> Add support for tracking dirty DAX entries in the struct address_space
>> radix tree. This tree is already used for dirty page writeback, and it
>> already supports the use of exceptional (non struct page*) entries.
>>
>> In order to properly track dirty DAX pages we will insert new exceptional
>> entries into the radix tree that represent dirty DAX PTE or PMD pages.
>
> I may get it wrong, but there is "struct page" for persistent memory after
> "[PATCH v4 00/18]get_user_pages() for dax pte and pmd mappings".
> So why not just add "struct page" to radix tree directly just like normal page cache?
>
> Then we don't need to deal with any exceptional entries and special writeback.
That "struct page" is optional and fsync/msync needs to operate in its absence.
On 12/31/2015 04:39 AM, Dan Williams wrote:
> On Wed, Dec 30, 2015 at 12:02 AM, Bob Liu <[email protected]> wrote:
>> Hi Ross,
>>
>> On 12/24/2015 03:39 AM, Ross Zwisler wrote:
>>> Add support for tracking dirty DAX entries in the struct address_space
>>> radix tree. This tree is already used for dirty page writeback, and it
>>> already supports the use of exceptional (non struct page*) entries.
>>>
>>> In order to properly track dirty DAX pages we will insert new exceptional
>>> entries into the radix tree that represent dirty DAX PTE or PMD pages.
>>
>> I may get it wrong, but there is "struct page" for persistent memory after
>> "[PATCH v4 00/18]get_user_pages() for dax pte and pmd mappings".
>> So why not just add "struct page" to radix tree directly just like normal page cache?
>>
>> Then we don't need to deal with any exceptional entries and special writeback.
>
> That "struct page" is optional and fsync/msync needs to operate in its absence.
>
Any special reason or scenario that "struct page" should not be enabled?
I didn't see any disadvantages if always enable "struct page" by force when using DAX model for pmem.
The benefits would be things can be more simple and less potential bugs because of smaller patches.
Happy New Year!
Bob
On Wed, Dec 30, 2015 at 7:28 PM, Bob Liu <[email protected]> wrote:
>
> On 12/31/2015 04:39 AM, Dan Williams wrote:
>> On Wed, Dec 30, 2015 at 12:02 AM, Bob Liu <[email protected]> wrote:
>>> Hi Ross,
>>>
>>> On 12/24/2015 03:39 AM, Ross Zwisler wrote:
>>>> Add support for tracking dirty DAX entries in the struct address_space
>>>> radix tree. This tree is already used for dirty page writeback, and it
>>>> already supports the use of exceptional (non struct page*) entries.
>>>>
>>>> In order to properly track dirty DAX pages we will insert new exceptional
>>>> entries into the radix tree that represent dirty DAX PTE or PMD pages.
>>>
>>> I may get it wrong, but there is "struct page" for persistent memory after
>>> "[PATCH v4 00/18]get_user_pages() for dax pte and pmd mappings".
>>> So why not just add "struct page" to radix tree directly just like normal page cache?
>>>
>>> Then we don't need to deal with any exceptional entries and special writeback.
>>
>> That "struct page" is optional and fsync/msync needs to operate in its absence.
>>
>
> Any special reason or scenario that "struct page" should not be enabled?
> I didn't see any disadvantages if always enable "struct page" by force when using DAX model for pmem.
> The benefits would be things can be more simple and less potential bugs because of smaller patches.
>
We can't enable struct page coverage by default.
The persistent memory capacity may be too large to allocate the memmap
array from DRAM. Allocating it from pmem reduces the size of the
device and we can't have a block device change sizes just by booting a
different kernel (any kernel less than 4.5). So, enabling struct page
must be an explicit action.
> Happy New Year!
Happy New Year!