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SubjectRe: [PATCH] Revert "f2fs: fix quota_sync failure due to f2fs_lock_op"
On 05/29, Chao Yu wrote:
> Under heavy fsstress, we may triggle panic while issuing discard,
> because __check_sit_bitmap() detects that discard command may earse
> valid data blocks, the root cause is as below race stack described,
> since we removed lock when flushing quota data, quota data writeback
> may race with write_checkpoint(), so that it causes inconsistency in
> between cached discard entry and segment bitmap.
>
> - f2fs_write_checkpoint
> - block_operations
> - set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH)
> - f2fs_flush_sit_entries
> - add_discard_addrs
> - __set_bit_le(i, (void *)de->discard_map);
> - f2fs_write_data_pages
> - f2fs_write_single_data_page
> : inode is quota one, cp_rwsem won't be locked
> - f2fs_do_write_data_page
> - f2fs_allocate_data_block
> - f2fs_wait_discard_bio
> : discard entry has not been added yet.
> - update_sit_entry
> - f2fs_clear_prefree_segments
> - f2fs_issue_discard
> : add discard entry
>
> This patch fixes this issue by reverting 435cbab95e39 ("f2fs: fix quota_sync
> failure due to f2fs_lock_op").
>
> Fixes: 435cbab95e39 ("f2fs: fix quota_sync failure due to f2fs_lock_op")

The previous patch fixes quota_sync gets EAGAIN all the time.
How about this? It seems this works for fsstress test.

---
fs/f2fs/segment.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index ebbadde6cbced..f67cffc38975e 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -3095,6 +3095,14 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
struct curseg_info *curseg = CURSEG_I(sbi, type);
bool put_pin_sem = false;

+ /*
+ * We need to wait for node_write to avoid block allocation during
+ * checkpoint. This can only happen to quota writes which can cause
+ * the below discard race condition.
+ */
+ if (IS_DATASEG(type))
+ down_write(&sbi->node_write);
+
if (type == CURSEG_COLD_DATA) {
/* GC during CURSEG_COLD_DATA_PINNED allocation */
if (down_read_trylock(&sbi->pin_sem)) {
@@ -3174,6 +3182,9 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,

if (put_pin_sem)
up_read(&sbi->pin_sem);
+
+ if (IS_DATASEG(type))
+ up_write(&sbi->node_write);
}

static void update_device_state(struct f2fs_io_info *fio)
--
2.27.0.rc0.183.gde8f92d652-goog
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