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authorYi Zhuang <zhuangyi1@huawei.com>2021-03-31 17:34:14 +0800
committerJaegeuk Kim <jaegeuk@kernel.org>2021-03-31 08:51:08 -0700
commitbe1ee45d51384161681ecf21085a42d316ae25f7 (patch)
tree335a25b42f22221b3fc26a59fcae5a01aceb7128
parent23738e74472f9c5f3a05a68724a2ccfba97d283d (diff)
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f2fs: Fix a hungtask problem in atomic write
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 <zhuangyi1@huawei.com> Reviewed-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
-rw-r--r--fs/f2fs/segment.c30
1 files changed, 17 insertions, 13 deletions
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 31ccea1378fa..c517e689a9a3 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)