From: Jin Xu <jinuxst...@gmail.com>
This patch fixes a deadlock bug that occurs quite often when there are
concurrent write and fsync on a same file.
Following is the simplified call trace when tasks get hung.
fsync thread:
- f2fs_sync_file
...
- f2fs_write_data_pages
...
- update_extent_cache
...
- update_inode
- wait_on_page_writeback
bdi writeback thread
- __writeback_single_inode
- f2fs_write_data_pages
- mutex_lock(sbi->writepages)
The deadlock happens when the fsync thread waits on a inode page that has
been added to the f2fs' cached bio sbi->bio[NODE], and unfortunately,
no one else could be able to submit the cached bio to block layer for
writeback. This is because the fsync thread already hold a sbi->fs_lock and
the sbi->writepages lock, causing the bdi thread being blocked when attempt
to write data pages for the same inode. At the same time, f2fs_gc thread
does not notice the situation and could not help. Even the sync syscall
gets blocked.
To fix it, we could submit the cached bio first before waiting on a inode page
that is being written back.
Signed-off-by: Jin Xu <jinuxst...@gmail.com>
---
fs/f2fs/f2fs.h | 2 ++
fs/f2fs/gc.c | 5 +----
fs/f2fs/inode.c | 3 ++-
fs/f2fs/segment.c | 9 +++++++++
4 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 467d42d..064d3f9 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1013,6 +1013,8 @@ void allocate_new_segments(struct f2fs_sb_info *);
struct page *get_sum_page(struct f2fs_sb_info *, unsigned int);
struct bio *f2fs_bio_alloc(struct block_device *, int);
void f2fs_submit_bio(struct f2fs_sb_info *, enum page_type, bool sync);
+void f2fs_wait_on_page_writeback(struct f2fs_sb_info *sbi,
+ struct page *page, enum page_type type, bool sync);
void write_meta_page(struct f2fs_sb_info *, struct page *);
void write_node_page(struct f2fs_sb_info *, struct page *, unsigned int,
block_t, block_t *);
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 35f9b1a..acfa411 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -508,10 +508,7 @@ static void move_data_page(struct inode *inode, struct
page *page, int gc_type)
} else {
struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
- if (PageWriteback(page)) {
- f2fs_submit_bio(sbi, DATA, true);
- wait_on_page_writeback(page);
- }
+ f2fs_wait_on_page_writeback(sbi, page, DATA, true);
if (clear_page_dirty_for_io(page) &&
S_ISDIR(inode->i_mode)) {
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 2b2d45d1..d42b85b 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -148,10 +148,11 @@ bad_inode:
void update_inode(struct inode *inode, struct page *node_page)
{
+ struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
struct f2fs_node *rn;
struct f2fs_inode *ri;
- wait_on_page_writeback(node_page);
+ f2fs_wait_on_page_writeback(sbi, node_page, NODE, false);
rn = page_address(node_page);
ri = &(rn->i);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a86d125..7056cc0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -702,6 +702,15 @@ alloc_new:
trace_f2fs_submit_write_page(page, blk_addr, type);
}
+void f2fs_wait_on_page_writeback(struct f2fs_sb_info *sbi,
+ struct page *page, enum page_type type, bool sync)
+{
+ if (PageWriteback(page)) {
+ f2fs_submit_bio(sbi, type, sync);
+ wait_on_page_writeback(page);
+ }
+}
+
static bool __has_curseg_space(struct f2fs_sb_info *sbi, int type)
{
struct curseg_info *curseg = CURSEG_I(sbi, type);
--
1.7.9.5
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