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SubjectRe: [PATCH] Revert "f2fs: fix quota_sync failure due to f2fs_lock_op"
On 05/30, Chao Yu wrote:
> On 2020/5/30 6:34, Jaegeuk Kim wrote:
> > 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.
> >

Then this?

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

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index ebbadde6cbced..ed11dcf2d69ed 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -3107,6 +3107,14 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
type = CURSEG_COLD_DATA;
}

+ /*
+ * 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);
+
down_read(&SM_I(sbi)->curseg_lock);

mutex_lock(&curseg->curseg_mutex);
@@ -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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