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Subject[PATCH 4.20 082/352] f2fs: fix race between write_checkpoint and write_begin
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 2866fb16d67992195b0526d19e65acb6640fb87f ]

The following race could lead to inconsistent SIT bitmap:

Task A Task B
====== ======
f2fs_write_checkpoint
block_operations
f2fs_lock_all
down_write(node_change)
down_write(node_write)
... sync ...
up_write(node_change)
f2fs_file_write_iter
set_inode_flag(FI_NO_PREALLOC)
......
f2fs_write_begin(index=0, has inline data)
prepare_write_begin
__do_map_lock(AIO) => down_read(node_change)
f2fs_convert_inline_page => update SIT
__do_map_lock(AIO) => up_read(node_change)
f2fs_flush_sit_entries <= inconsistent SIT
finish write checkpoint
sudden-power-off

If SPO occurs after checkpoint is finished, SIT bitmap will be set
incorrectly.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/data.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 17049b030b6c..e90ca6aa3a00 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2326,6 +2326,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
bool locked = false;
struct extent_info ei = {0,0,0};
int err = 0;
+ int flag;

/*
* we already allocated all the blocks, so we don't need to get
@@ -2335,9 +2336,15 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
!is_inode_flag_set(inode, FI_NO_PREALLOC))
return 0;

+ /* f2fs_lock_op avoids race between write CP and convert_inline_page */
+ if (f2fs_has_inline_data(inode) && pos + len > MAX_INLINE_DATA(inode))
+ flag = F2FS_GET_BLOCK_DEFAULT;
+ else
+ flag = F2FS_GET_BLOCK_PRE_AIO;
+
if (f2fs_has_inline_data(inode) ||
(pos & PAGE_MASK) >= i_size_read(inode)) {
- __do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, true);
+ __do_map_lock(sbi, flag, true);
locked = true;
}
restart:
@@ -2375,6 +2382,7 @@ restart:
f2fs_put_dnode(&dn);
__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO,
true);
+ WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);
locked = true;
goto restart;
}
@@ -2388,7 +2396,7 @@ out:
f2fs_put_dnode(&dn);
unlock_out:
if (locked)
- __do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, false);
+ __do_map_lock(sbi, flag, false);
return err;
}

--
2.19.1


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