In the cache writing process, if it is an atomic file, increase the page
count of F2FS_WB_CP_DATA, otherwise increase the page count of
F2FS_WB_DATA.
When you step into the hook branch due to insufficient memory in
f2fs_write_begin, f2fs_drop_inmem_pages_all will be called to traverse
all atomic inodes and clear the FI_ATOMIC_FILE mark of all atomic files.
In f2fs_drop_inmem_pages，first acquire the inmem_lock , revoke all the
inmem_pages, and then clear the FI_ATOMIC_FILE mark. Before this mark is
cleared, other threads may hold inmem_lock to add inmem_pages to the inode
that has just been emptied inmem_pages, and increase the page count of
F2FS_WB_CP_DATA.
When the IO returns, it is found that the FI_ATOMIC_FILE flag is cleared
by f2fs_drop_inmem_pages_all, and f2fs_is_atomic_file returns false,which
causes the page count of F2FS_WB_DATA to be decremented. The page count of
F2FS_WB_CP_DATA cannot be cleared. Finally, hungtask is triggered in
f2fs_wait_on_all_pages because get_pages will never return zero.
process A: process B:
f2fs_drop_inmem_pages_all
->f2fs_drop_inmem_pages of inode#1
->mutex_lock(&fi->inmem_lock)
->__revoke_inmem_pages of inode#1 f2fs_ioc_commit_atomic_write
->mutex_unlock(&fi->inmem_lock) ->f2fs_commit_inmem_pages of inode#1
->mutex_lock(&fi->inmem_lock)
->__f2fs_commit_inmem_pages
->f2fs_do_write_data_page
->f2fs_outplace_write_data
->do_write_page
->f2fs_submit_page_write
->inc_page_count(sbi, F2FS_WB_CP_DATA )
->mutex_unlock(&fi->inmem_lock)
->spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
->clear_inode_flag(inode, FI_ATOMIC_FILE)
->spin_unlock(&sbi->inode_lock[ATOMIC_FILE])
f2fs_write_end_io
->dec_page_count(sbi, F2FS_WB_DATA );
We can fix the problem by putting the action of clearing the FI_ATOMIC_FILE
mark into the inmem_lock lock. This operation can ensure that no one will
submit the inmem pages before the FI_ATOMIC_FILE mark is cleared, so that
there will be no atomic writes waiting for writeback.
Fixes: 57864ae5ce3a ("f2fs: limit # of inmemory pages")
Signed-off-by: Yi Zhuang <[email protected]>
---
fs/f2fs/segment.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c2866561263e..e4627fe93390 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -324,23 +324,27 @@ void f2fs_drop_inmem_pages(struct inode *inode)
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct f2fs_inode_info *fi = F2FS_I(inode);
- while (!list_empty(&fi->inmem_pages)) {
+ do {
mutex_lock(&fi->inmem_lock);
+ if (list_empty(&fi->inmem_pages)) {
+ fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
+
+ spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
+ if (!list_empty(&fi->inmem_ilist))
+ list_del_init(&fi->inmem_ilist);
+ if (f2fs_is_atomic_file(inode)) {
+ clear_inode_flag(inode, FI_ATOMIC_FILE);
+ sbi->atomic_files--;
+ }
+ spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+
+ mutex_unlock(&fi->inmem_lock);
+ break;
+ }
__revoke_inmem_pages(inode, &fi->inmem_pages,
true, false, true);
mutex_unlock(&fi->inmem_lock);
- }
-
- fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
-
- spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
- if (!list_empty(&fi->inmem_ilist))
- list_del_init(&fi->inmem_ilist);
- if (f2fs_is_atomic_file(inode)) {
- clear_inode_flag(inode, FI_ATOMIC_FILE);
- sbi->atomic_files--;
- }
- spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
+ } while (1);
}
void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
--
2.26.0.106.g9fadedd
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