This is a BUG_ON issue as follows when running xfstest-generic-503:
WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
Modules linked in:
CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
Call Trace:
evict+0x129/0x2d0
dispose_list+0x4f/0xb0
evict_inodes+0x204/0x230
generic_shutdown_super+0x5b/0x1e0
kill_block_super+0x29/0x80
kill_f2fs_super+0xe6/0x140
deactivate_locked_super+0x44/0xc0
deactivate_super+0x79/0x90
cleanup_mnt+0x114/0x1a0
__cleanup_mnt+0x16/0x20
task_work_run+0x98/0x100
exit_to_user_mode_prepare+0x3d0/0x3e0
syscall_exit_to_user_mode+0x12/0x30
do_syscall_64+0x42/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
Function flow analysis when BUG occurs:
f2fs_fallocate mmap
do_page_fault
pte_spinlock // ---lock_pte
do_wp_page
wp_page_shared
pte_unmap_unlock // unlock_pte
do_page_mkwrite
f2fs_vm_page_mkwrite
down_read(i_mmap_sem)
lock_page
if (PageMappedToDisk(page))
goto out;
// set_page_dirty --NOT RUN
out: up_read(i_mmap_sem)
lock_page
finish_mkwrite_fault // unlock_pte
f2fs_collapse_range
down_write(i_mmap_sem)
truncate_pagecache
unmap_mapping_pages
i_mmap_lock_write // down_write(i_mmap_rwsem)
......
zap_pte_range
pte_offset_map_lock // ---lock_pte
f2fs_set_data_page_dirty
if (!PageDirty(page)) {
fault_dirty_shared_page
f2fs_set_data_page_dirty
if (!PageDirty(page)) {
__set_page_dirty_nobuffer
f2fs_update_dirty_page // ++
}
unlock_page
__set_page_dirty_nobuffers
f2fs_update_dirty_page // page count++
}
pte_unmap_unlock // --unlock_pte
i_mmap_unlock_write // up_write(i_mmap_rwsem)
truncate_inode_pages
up_write(i_mmap_sem)
When race happens between mmap-do_page_fault-wp_page_shared and
fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
function set_page_dirty without page lock. Besides, though
truncate_pagecache has immap and pte lock, wp_page_shared calls
fault_dirty_shared_page without any. In this case, two threads race
in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
but the count is added TWICE by calling f2fs_update_dirty_page.
Thus the count of dirty page cannot accord with the real dirty pages.
Following is the solution to in case of race happens without any lock.
If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
lock area, page will already be dirtied when running into
fault_dirty_shared_page-f2fs_set_data_page_dirty.
The count of dirty page will not be increased wrong times.
Signed-off-by: Shuqi Zhang <[email protected]>
---
fs/f2fs/file.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index ce4905a073b3..d837359a9c00 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
* check to see if the page is mapped already (no holes)
*/
if (PageMappedToDisk(page))
- goto out_sem;
+ goto set_dirty;
/* page is wholly or partially inside EOF */
if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
@@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
offset = i_size_read(inode) & ~PAGE_MASK;
zero_user_segment(page, offset, PAGE_SIZE);
}
- set_page_dirty(page);
- if (!PageUptodate(page))
- SetPageUptodate(page);
f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
- f2fs_update_time(sbi, REQ_TIME);
+set_dirty:
trace_f2fs_vm_page_mkwrite(page, DATA);
+ set_page_dirty(page);
+ if (!PageUptodate(page))
+ SetPageUptodate(page);
+ f2fs_update_time(sbi, REQ_TIME);
out_sem:
filemap_invalidate_unlock_shared(inode->i_mapping);
--
2.25.1
On 2022/8/15 16:15, Shuqi Zhang wrote:
> This is a BUG_ON issue as follows when running xfstest-generic-503:
> WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
> Modules linked in:
> CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
>
> Call Trace:
> evict+0x129/0x2d0
> dispose_list+0x4f/0xb0
> evict_inodes+0x204/0x230
> generic_shutdown_super+0x5b/0x1e0
> kill_block_super+0x29/0x80
> kill_f2fs_super+0xe6/0x140
> deactivate_locked_super+0x44/0xc0
> deactivate_super+0x79/0x90
> cleanup_mnt+0x114/0x1a0
> __cleanup_mnt+0x16/0x20
> task_work_run+0x98/0x100
> exit_to_user_mode_prepare+0x3d0/0x3e0
> syscall_exit_to_user_mode+0x12/0x30
> do_syscall_64+0x42/0x80
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> Function flow analysis when BUG occurs:
> f2fs_fallocate mmap
> do_page_fault
> pte_spinlock // ---lock_pte
> do_wp_page
> wp_page_shared
> pte_unmap_unlock // unlock_pte
> do_page_mkwrite
> f2fs_vm_page_mkwrite
> down_read(i_mmap_sem)
> lock_page
> if (PageMappedToDisk(page))
> goto out;
> // set_page_dirty --NOT RUN
> out: up_read(i_mmap_sem)
> lock_page
> finish_mkwrite_fault // unlock_pte
> f2fs_collapse_range
> down_write(i_mmap_sem)
> truncate_pagecache
> unmap_mapping_pages
> i_mmap_lock_write // down_write(i_mmap_rwsem)
> ......
> zap_pte_range
> pte_offset_map_lock // ---lock_pte
> f2fs_set_data_page_dirty
I didn't get it, why zap_pte_range() can set page dirty w/o lock_page?
I found it's very easy to reproduce this bug, but previously I never saw this...
is there any code udpate around truncate_pagecache()?
Thanks,
> if (!PageDirty(page)) {
> fault_dirty_shared_page
> f2fs_set_data_page_dirty
> if (!PageDirty(page)) {
> __set_page_dirty_nobuffer
> f2fs_update_dirty_page // ++
> }
> unlock_page
> __set_page_dirty_nobuffers
> f2fs_update_dirty_page // page count++
> }
> pte_unmap_unlock // --unlock_pte
> i_mmap_unlock_write // up_write(i_mmap_rwsem)
> truncate_inode_pages
> up_write(i_mmap_sem)
>
> When race happens between mmap-do_page_fault-wp_page_shared and
> fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
> function set_page_dirty without page lock. Besides, though
> truncate_pagecache has immap and pte lock, wp_page_shared calls
> fault_dirty_shared_page without any. In this case, two threads race
> in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
> but the count is added TWICE by calling f2fs_update_dirty_page.
> Thus the count of dirty page cannot accord with the real dirty pages.
>
> Following is the solution to in case of race happens without any lock.
> If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
> lock area, page will already be dirtied when running into
> fault_dirty_shared_page-f2fs_set_data_page_dirty.
> The count of dirty page will not be increased wrong times.
>
> Signed-off-by: Shuqi Zhang <[email protected]>
> ---
> fs/f2fs/file.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index ce4905a073b3..d837359a9c00 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> * check to see if the page is mapped already (no holes)
> */
> if (PageMappedToDisk(page))
> - goto out_sem;
> + goto set_dirty;
>
> /* page is wholly or partially inside EOF */
> if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
> @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> offset = i_size_read(inode) & ~PAGE_MASK;
> zero_user_segment(page, offset, PAGE_SIZE);
> }
> - set_page_dirty(page);
> - if (!PageUptodate(page))
> - SetPageUptodate(page);
>
> f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
> - f2fs_update_time(sbi, REQ_TIME);
>
> +set_dirty:
> trace_f2fs_vm_page_mkwrite(page, DATA);
> + set_page_dirty(page);
> + if (!PageUptodate(page))
> + SetPageUptodate(page);
> + f2fs_update_time(sbi, REQ_TIME);
> out_sem:
> filemap_invalidate_unlock_shared(inode->i_mapping);
>
On 08/20, Chao Yu wrote:
> On 2022/8/15 16:15, Shuqi Zhang wrote:
> > This is a BUG_ON issue as follows when running xfstest-generic-503:
> > WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
> > Modules linked in:
> > CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
> >
> > Call Trace:
> > evict+0x129/0x2d0
> > dispose_list+0x4f/0xb0
> > evict_inodes+0x204/0x230
> > generic_shutdown_super+0x5b/0x1e0
> > kill_block_super+0x29/0x80
> > kill_f2fs_super+0xe6/0x140
> > deactivate_locked_super+0x44/0xc0
> > deactivate_super+0x79/0x90
> > cleanup_mnt+0x114/0x1a0
> > __cleanup_mnt+0x16/0x20
> > task_work_run+0x98/0x100
> > exit_to_user_mode_prepare+0x3d0/0x3e0
> > syscall_exit_to_user_mode+0x12/0x30
> > do_syscall_64+0x42/0x80
> > entry_SYSCALL_64_after_hwframe+0x46/0xb0
> >
> > Function flow analysis when BUG occurs:
> > f2fs_fallocate mmap
> > do_page_fault
> > pte_spinlock // ---lock_pte
> > do_wp_page
> > wp_page_shared
> > pte_unmap_unlock // unlock_pte
> > do_page_mkwrite
> > f2fs_vm_page_mkwrite
> > down_read(i_mmap_sem)
> > lock_page
> > if (PageMappedToDisk(page))
> > goto out;
> > // set_page_dirty --NOT RUN
> > out: up_read(i_mmap_sem)
> > lock_page
> > finish_mkwrite_fault // unlock_pte
> > f2fs_collapse_range
> > down_write(i_mmap_sem)
> > truncate_pagecache
> > unmap_mapping_pages
> > i_mmap_lock_write // down_write(i_mmap_rwsem)
> > ......
> > zap_pte_range
> > pte_offset_map_lock // ---lock_pte
> > f2fs_set_data_page_dirty
>
> I didn't get it, why zap_pte_range() can set page dirty w/o lock_page?
>
> I found it's very easy to reproduce this bug, but previously I never saw this...
> is there any code udpate around truncate_pagecache()?
Found this.
2637 * The caller must ensure this doesn't race with truncation. Most will
2638 * simply hold the folio lock, but e.g. zap_pte_range() calls with the
2639 * folio mapped and the pte lock held, which also locks out truncation.
2640 */
2641 bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
2642 {
>
> Thanks,
>
> > if (!PageDirty(page)) {
> > fault_dirty_shared_page
> > f2fs_set_data_page_dirty
> > if (!PageDirty(page)) {
> > __set_page_dirty_nobuffer
> > f2fs_update_dirty_page // ++
> > }
> > unlock_page
> > __set_page_dirty_nobuffers
> > f2fs_update_dirty_page // page count++
> > }
> > pte_unmap_unlock // --unlock_pte
> > i_mmap_unlock_write // up_write(i_mmap_rwsem)
> > truncate_inode_pages
> > up_write(i_mmap_sem)
> >
> > When race happens between mmap-do_page_fault-wp_page_shared and
> > fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
> > function set_page_dirty without page lock. Besides, though
> > truncate_pagecache has immap and pte lock, wp_page_shared calls
> > fault_dirty_shared_page without any. In this case, two threads race
> > in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
> > but the count is added TWICE by calling f2fs_update_dirty_page.
> > Thus the count of dirty page cannot accord with the real dirty pages.
> >
> > Following is the solution to in case of race happens without any lock.
> > If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
> > lock area, page will already be dirtied when running into
> > fault_dirty_shared_page-f2fs_set_data_page_dirty.
> > The count of dirty page will not be increased wrong times.
> >
> > Signed-off-by: Shuqi Zhang <[email protected]>
> > ---
> > fs/f2fs/file.c | 11 ++++++-----
> > 1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index ce4905a073b3..d837359a9c00 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> > * check to see if the page is mapped already (no holes)
> > */
> > if (PageMappedToDisk(page))
> > - goto out_sem;
> > + goto set_dirty;
> > /* page is wholly or partially inside EOF */
> > if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
> > @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> > offset = i_size_read(inode) & ~PAGE_MASK;
> > zero_user_segment(page, offset, PAGE_SIZE);
> > }
> > - set_page_dirty(page);
> > - if (!PageUptodate(page))
> > - SetPageUptodate(page);
> > f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
> > - f2fs_update_time(sbi, REQ_TIME);
> > +set_dirty:
> > trace_f2fs_vm_page_mkwrite(page, DATA);
> > + set_page_dirty(page);
> > + if (!PageUptodate(page))
> > + SetPageUptodate(page);
> > + f2fs_update_time(sbi, REQ_TIME);
> > out_sem:
> > filemap_invalidate_unlock_shared(inode->i_mapping);
On 08/20, Jaegeuk Kim wrote:
> On 08/20, Chao Yu wrote:
> > On 2022/8/15 16:15, Shuqi Zhang wrote:
> > > This is a BUG_ON issue as follows when running xfstest-generic-503:
> > > WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
> > > Modules linked in:
> > > CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
> > >
> > > Call Trace:
> > > evict+0x129/0x2d0
> > > dispose_list+0x4f/0xb0
> > > evict_inodes+0x204/0x230
> > > generic_shutdown_super+0x5b/0x1e0
> > > kill_block_super+0x29/0x80
> > > kill_f2fs_super+0xe6/0x140
> > > deactivate_locked_super+0x44/0xc0
> > > deactivate_super+0x79/0x90
> > > cleanup_mnt+0x114/0x1a0
> > > __cleanup_mnt+0x16/0x20
> > > task_work_run+0x98/0x100
> > > exit_to_user_mode_prepare+0x3d0/0x3e0
> > > syscall_exit_to_user_mode+0x12/0x30
> > > do_syscall_64+0x42/0x80
> > > entry_SYSCALL_64_after_hwframe+0x46/0xb0
> > >
> > > Function flow analysis when BUG occurs:
> > > f2fs_fallocate mmap
> > > do_page_fault
> > > pte_spinlock // ---lock_pte
> > > do_wp_page
> > > wp_page_shared
> > > pte_unmap_unlock // unlock_pte
> > > do_page_mkwrite
> > > f2fs_vm_page_mkwrite
> > > down_read(i_mmap_sem)
> > > lock_page
> > > if (PageMappedToDisk(page))
> > > goto out;
> > > // set_page_dirty --NOT RUN
> > > out: up_read(i_mmap_sem)
> > > lock_page
> > > finish_mkwrite_fault // unlock_pte
> > > f2fs_collapse_range
> > > down_write(i_mmap_sem)
> > > truncate_pagecache
> > > unmap_mapping_pages
> > > i_mmap_lock_write // down_write(i_mmap_rwsem)
> > > ......
> > > zap_pte_range
> > > pte_offset_map_lock // ---lock_pte
> > > f2fs_set_data_page_dirty
> >
> > I didn't get it, why zap_pte_range() can set page dirty w/o lock_page?
> >
> > I found it's very easy to reproduce this bug, but previously I never saw this...
> > is there any code udpate around truncate_pagecache()?
>
> Found this.
>
> 2637 * The caller must ensure this doesn't race with truncation. Most will
> 2638 * simply hold the folio lock, but e.g. zap_pte_range() calls with the
> 2639 * folio mapped and the pte lock held, which also locks out truncation.
> 2640 */
> 2641 bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
> 2642 {
>
> >
> > Thanks,
> >
> > > if (!PageDirty(page)) {
> > > fault_dirty_shared_page
> > > f2fs_set_data_page_dirty
> > > if (!PageDirty(page)) {
> > > __set_page_dirty_nobuffer
> > > f2fs_update_dirty_page // ++
> > > }
> > > unlock_page
> > > __set_page_dirty_nobuffers
> > > f2fs_update_dirty_page // page count++
> > > }
> > > pte_unmap_unlock // --unlock_pte
> > > i_mmap_unlock_write // up_write(i_mmap_rwsem)
> > > truncate_inode_pages
> > > up_write(i_mmap_sem)
> > >
> > > When race happens between mmap-do_page_fault-wp_page_shared and
> > > fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
> > > function set_page_dirty without page lock. Besides, though
> > > truncate_pagecache has immap and pte lock, wp_page_shared calls
> > > fault_dirty_shared_page without any. In this case, two threads race
> > > in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
> > > but the count is added TWICE by calling f2fs_update_dirty_page.
> > > Thus the count of dirty page cannot accord with the real dirty pages.
> > >
> > > Following is the solution to in case of race happens without any lock.
> > > If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
> > > lock area, page will already be dirtied when running into
> > > fault_dirty_shared_page-f2fs_set_data_page_dirty.
> > > The count of dirty page will not be increased wrong times.
> > >
> > > Signed-off-by: Shuqi Zhang <[email protected]>
> > > ---
> > > fs/f2fs/file.c | 11 ++++++-----
> > > 1 file changed, 6 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > index ce4905a073b3..d837359a9c00 100644
> > > --- a/fs/f2fs/file.c
> > > +++ b/fs/f2fs/file.c
> > > @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> > > * check to see if the page is mapped already (no holes)
> > > */
> > > if (PageMappedToDisk(page))
> > > - goto out_sem;
> > > + goto set_dirty;
> > > /* page is wholly or partially inside EOF */
> > > if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
> > > @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> > > offset = i_size_read(inode) & ~PAGE_MASK;
> > > zero_user_segment(page, offset, PAGE_SIZE);
> > > }
> > > - set_page_dirty(page);
> > > - if (!PageUptodate(page))
> > > - SetPageUptodate(page);
> > > f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
> > > - f2fs_update_time(sbi, REQ_TIME);
> > > +set_dirty:
> > > trace_f2fs_vm_page_mkwrite(page, DATA);
> > > + set_page_dirty(page);
> > > + if (!PageUptodate(page))
> > > + SetPageUptodate(page);
Actually we don't need to call SetPageUptodate() since set_page_dirty() should
do? And, it seems the call stack is out-dated as well.
By the way, do we just need to get the right count by this?
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3697,8 +3697,7 @@ static bool f2fs_dirty_data_folio(struct address_space *mapping,
folio_mark_uptodate(folio);
BUG_ON(folio_test_swapcache(folio));
- if (!folio_test_dirty(folio)) {
- filemap_dirty_folio(mapping, folio);
+ if (filemap_dirty_folio(mapping, folio)) {
f2fs_update_dirty_folio(inode, folio);
return true;
}
> > > + f2fs_update_time(sbi, REQ_TIME);
> > > out_sem:
> > > filemap_invalidate_unlock_shared(inode->i_mapping);
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
On 08/21, Jaegeuk Kim wrote:
> On 08/20, Jaegeuk Kim wrote:
>> On 08/20, Chao Yu wrote:
>>> On 2022/8/15 16:15, Shuqi Zhang wrote:
>>>> This is a BUG_ON issue as follows when running xfstest-generic-503:
>>>> WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
>>>> Modules linked in:
>>>> CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
>>>>
>>>> Call Trace:
>>>> evict+0x129/0x2d0
>>>> dispose_list+0x4f/0xb0
>>>> evict_inodes+0x204/0x230
>>>> generic_shutdown_super+0x5b/0x1e0
>>>> kill_block_super+0x29/0x80
>>>> kill_f2fs_super+0xe6/0x140
>>>> deactivate_locked_super+0x44/0xc0
>>>> deactivate_super+0x79/0x90
>>>> cleanup_mnt+0x114/0x1a0
>>>> __cleanup_mnt+0x16/0x20
>>>> task_work_run+0x98/0x100
>>>> exit_to_user_mode_prepare+0x3d0/0x3e0
>>>> syscall_exit_to_user_mode+0x12/0x30
>>>> do_syscall_64+0x42/0x80
>>>> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>>>
>>>> Function flow analysis when BUG occurs:
>>>> f2fs_fallocate mmap
>>>> do_page_fault
>>>> pte_spinlock // ---lock_pte
>>>> do_wp_page
>>>> wp_page_shared
>>>> pte_unmap_unlock // unlock_pte
>>>> do_page_mkwrite
>>>> f2fs_vm_page_mkwrite
>>>> down_read(i_mmap_sem)
>>>> lock_page
>>>> if (PageMappedToDisk(page))
>>>> goto out;
>>>> // set_page_dirty --NOT RUN
>>>> out: up_read(i_mmap_sem)
>>>> lock_page
>>>> finish_mkwrite_fault // unlock_pte
>>>> f2fs_collapse_range
>>>> down_write(i_mmap_sem)
>>>> truncate_pagecache
>>>> unmap_mapping_pages
>>>> i_mmap_lock_write // down_write(i_mmap_rwsem)
>>>> ......
>>>> zap_pte_range
>>>> pte_offset_map_lock // ---lock_pte
>>>> f2fs_set_data_page_dirty
>>> I didn't get it, why zap_pte_range() can set page dirty w/o lock_page?
>>>
>>> I found it's very easy to reproduce this bug, but previously I never saw this...
>>> is there any code udpate around truncate_pagecache()?
>> Found this.
>>
>> 2637 * The caller must ensure this doesn't race with truncation. Most will
>> 2638 * simply hold the folio lock, but e.g. zap_pte_range() calls with the
>> 2639 * folio mapped and the pte lock held, which also locks out truncation.
>> 2640 */
>> 2641 bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
>> 2642 {
>>
>>> Thanks,
>>>
>>>> if (!PageDirty(page)) {
>>>> fault_dirty_shared_page
>>>> f2fs_set_data_page_dirty
>>>> if (!PageDirty(page)) {
>>>> __set_page_dirty_nobuffer
>>>> f2fs_update_dirty_page // ++
>>>> }
>>>> unlock_page
>>>> __set_page_dirty_nobuffers
>>>> f2fs_update_dirty_page // page count++
>>>> }
>>>> pte_unmap_unlock // --unlock_pte
>>>> i_mmap_unlock_write // up_write(i_mmap_rwsem)
>>>> truncate_inode_pages
>>>> up_write(i_mmap_sem)
>>>>
>>>> When race happens between mmap-do_page_fault-wp_page_shared and
>>>> fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
>>>> function set_page_dirty without page lock. Besides, though
>>>> truncate_pagecache has immap and pte lock, wp_page_shared calls
>>>> fault_dirty_shared_page without any. In this case, two threads race
>>>> in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
>>>> but the count is added TWICE by calling f2fs_update_dirty_page.
>>>> Thus the count of dirty page cannot accord with the real dirty pages.
>>>>
>>>> Following is the solution to in case of race happens without any lock.
>>>> If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
>>>> lock area, page will already be dirtied when running into
>>>> fault_dirty_shared_page-f2fs_set_data_page_dirty.
>>>> The count of dirty page will not be increased wrong times.
>>>>
>>>> Signed-off-by: Shuqi Zhang <[email protected]>
>>>> ---
>>>> fs/f2fs/file.c | 11 ++++++-----
>>>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index ce4905a073b3..d837359a9c00 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>>>> * check to see if the page is mapped already (no holes)
>>>> */
>>>> if (PageMappedToDisk(page))
>>>> - goto out_sem;
>>>> + goto set_dirty;
>>>> /* page is wholly or partially inside EOF */
>>>> if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
>>>> @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>>>> offset = i_size_read(inode) & ~PAGE_MASK;
>>>> zero_user_segment(page, offset, PAGE_SIZE);
>>>> }
>>>> - set_page_dirty(page);
>>>> - if (!PageUptodate(page))
>>>> - SetPageUptodate(page);
>>>> f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
>>>> - f2fs_update_time(sbi, REQ_TIME);
>>>> +set_dirty:
>>>> trace_f2fs_vm_page_mkwrite(page, DATA);
>>>> + set_page_dirty(page);
>>>> + if (!PageUptodate(page))
>>>> + SetPageUptodate(page);
> Actually we don't need to call SetPageUptodate() since set_page_dirty() should
> do? And, it seems the call stack is out-dated as well.
>
> By the way, do we just need to get the right count by this?
>
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3697,8 +3697,7 @@ static bool f2fs_dirty_data_folio(struct address_space *mapping,
> folio_mark_uptodate(folio);
> BUG_ON(folio_test_swapcache(folio));
>
> - if (!folio_test_dirty(folio)) {
> - filemap_dirty_folio(mapping, folio);
> + if (filemap_dirty_folio(mapping, folio)) {
> f2fs_update_dirty_folio(inode, folio);
> return true;
> }
Yes, this patch seems a better one. I will send a PATCH-v2 about it.
Thanks,
>>>> + f2fs_update_time(sbi, REQ_TIME);
>>>> out_sem:
>>>> filemap_invalidate_unlock_shared(inode->i_mapping);
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
On 2022/8/21 6:19, Jaegeuk Kim wrote:
> On 08/20, Jaegeuk Kim wrote:
>> On 08/20, Chao Yu wrote:
>>> On 2022/8/15 16:15, Shuqi Zhang wrote:
>>>> This is a BUG_ON issue as follows when running xfstest-generic-503:
>>>> WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
>>>> Modules linked in:
>>>> CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
>>>>
>>>> Call Trace:
>>>> evict+0x129/0x2d0
>>>> dispose_list+0x4f/0xb0
>>>> evict_inodes+0x204/0x230
>>>> generic_shutdown_super+0x5b/0x1e0
>>>> kill_block_super+0x29/0x80
>>>> kill_f2fs_super+0xe6/0x140
>>>> deactivate_locked_super+0x44/0xc0
>>>> deactivate_super+0x79/0x90
>>>> cleanup_mnt+0x114/0x1a0
>>>> __cleanup_mnt+0x16/0x20
>>>> task_work_run+0x98/0x100
>>>> exit_to_user_mode_prepare+0x3d0/0x3e0
>>>> syscall_exit_to_user_mode+0x12/0x30
>>>> do_syscall_64+0x42/0x80
>>>> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>>>
>>>> Function flow analysis when BUG occurs:
>>>> f2fs_fallocate mmap
>>>> do_page_fault
>>>> pte_spinlock // ---lock_pte
>>>> do_wp_page
>>>> wp_page_shared
>>>> pte_unmap_unlock // unlock_pte
>>>> do_page_mkwrite
>>>> f2fs_vm_page_mkwrite
>>>> down_read(i_mmap_sem)
>>>> lock_page
>>>> if (PageMappedToDisk(page))
>>>> goto out;
>>>> // set_page_dirty --NOT RUN
>>>> out: up_read(i_mmap_sem)
>>>> lock_page
>>>> finish_mkwrite_fault // unlock_pte
>>>> f2fs_collapse_range
>>>> down_write(i_mmap_sem)
>>>> truncate_pagecache
>>>> unmap_mapping_pages
>>>> i_mmap_lock_write // down_write(i_mmap_rwsem)
>>>> ......
>>>> zap_pte_range
>>>> pte_offset_map_lock // ---lock_pte
>>>> f2fs_set_data_page_dirty
>>>
>>> I didn't get it, why zap_pte_range() can set page dirty w/o lock_page?
>>>
>>> I found it's very easy to reproduce this bug, but previously I never saw this...
>>> is there any code udpate around truncate_pagecache()?
>>
>> Found this.
>>
>> 2637 * The caller must ensure this doesn't race with truncation. Most will
>> 2638 * simply hold the folio lock, but e.g. zap_pte_range() calls with the
>> 2639 * folio mapped and the pte lock held, which also locks out truncation.
>> 2640 */
>> 2641 bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
>> 2642 {
>>
>>>
>>> Thanks,
>>>
>>>> if (!PageDirty(page)) {
>>>> fault_dirty_shared_page
>>>> f2fs_set_data_page_dirty
>>>> if (!PageDirty(page)) {
>>>> __set_page_dirty_nobuffer
>>>> f2fs_update_dirty_page // ++
>>>> }
>>>> unlock_page
>>>> __set_page_dirty_nobuffers
>>>> f2fs_update_dirty_page // page count++
>>>> }
>>>> pte_unmap_unlock // --unlock_pte
>>>> i_mmap_unlock_write // up_write(i_mmap_rwsem)
>>>> truncate_inode_pages
>>>> up_write(i_mmap_sem)
>>>>
>>>> When race happens between mmap-do_page_fault-wp_page_shared and
>>>> fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
>>>> function set_page_dirty without page lock. Besides, though
>>>> truncate_pagecache has immap and pte lock, wp_page_shared calls
>>>> fault_dirty_shared_page without any. In this case, two threads race
>>>> in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE,
>>>> but the count is added TWICE by calling f2fs_update_dirty_page.
>>>> Thus the count of dirty page cannot accord with the real dirty pages.
>>>>
>>>> Following is the solution to in case of race happens without any lock.
>>>> If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap
>>>> lock area, page will already be dirtied when running into
>>>> fault_dirty_shared_page-f2fs_set_data_page_dirty.
>>>> The count of dirty page will not be increased wrong times.
>>>>
>>>> Signed-off-by: Shuqi Zhang <[email protected]>
>>>> ---
>>>> fs/f2fs/file.c | 11 ++++++-----
>>>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index ce4905a073b3..d837359a9c00 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>>>> * check to see if the page is mapped already (no holes)
>>>> */
>>>> if (PageMappedToDisk(page))
>>>> - goto out_sem;
>>>> + goto set_dirty;
>>>> /* page is wholly or partially inside EOF */
>>>> if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
>>>> @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>>>> offset = i_size_read(inode) & ~PAGE_MASK;
>>>> zero_user_segment(page, offset, PAGE_SIZE);
>>>> }
>>>> - set_page_dirty(page);
>>>> - if (!PageUptodate(page))
>>>> - SetPageUptodate(page);
>>>> f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE);
>>>> - f2fs_update_time(sbi, REQ_TIME);
>>>> +set_dirty:
>>>> trace_f2fs_vm_page_mkwrite(page, DATA);
>>>> + set_page_dirty(page);
>>>> + if (!PageUptodate(page))
>>>> + SetPageUptodate(page);
>
> Actually we don't need to call SetPageUptodate() since set_page_dirty() should
> do? And, it seems the call stack is out-dated as well.
>
> By the way, do we just need to get the right count by this?
>
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3697,8 +3697,7 @@ static bool f2fs_dirty_data_folio(struct address_space *mapping,
> folio_mark_uptodate(folio);
> BUG_ON(folio_test_swapcache(folio));
>
> - if (!folio_test_dirty(folio)) {
> - filemap_dirty_folio(mapping, folio);
> + if (filemap_dirty_folio(mapping, folio)) {
Agreed, how about checking return value of filemap_dirty_folio() in
f2fs_dirty_{meta,node}_folio as well for cleanup.
> f2fs_update_dirty_folio(inode, folio);
> return true;
I suspect we may still suffer from below race condition? due to we will access/update
page private stuff w/o page lock in zap_pte_range.
- zap_pte_range - f2fs_defragment_range
- f2fs_dirty_data_folio
- f2fs_update_dirty_folio - lock_page
- set_page_private_reference - set_page_private_gcing
Thanks,
> }
>
>>>> + f2fs_update_time(sbi, REQ_TIME);
>>>> out_sem:
>>>> filemap_invalidate_unlock_shared(inode->i_mapping);
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel