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Message-ID: <20250912100650.3594565-1-wangzijie1@honor.com>
Date: Fri, 12 Sep 2025 18:06:50 +0800
From: wangzijie <wangzijie1@...or.com>
To: <chao@...nel.org>
CC: <feng.han@...or.com>, <jaegeuk@...nel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
<wangzijie1@...or.com>
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: fix wrong extent_info data for precache extents
>On 9/12/2025 11:36 AM, wangzijie wrote:
>>> On 9/11/2025 5:07 PM, wangzijie wrote:
>>>>> On 9/10/25 21:58, wangzijie wrote:
>>>>>> When the data layout is like this:
>>>>>> dnode1: dnode2:
>>>>>> [0] A [0] NEW_ADDR
>>>>>> [1] A+1 [1] 0x0
>>>>>> ... ....
>>>>>> [1016] A+1016
>>>>>> [1017] B (B!=A+1017) [1017] 0x0
>>>>>>
>>>>>> We can build this kind of layout by following steps(with i_extra_isize:36):
>>>>>> ./f2fs_io write 1 0 1881 rand dsync testfile
>>>>>> ./f2fs_io write 1 1881 1 rand buffered testfile
>>>>>> ./f2fs_io fallocate 0 7708672 4096 testfile
>>>>>>
>>>>>> And when we map first data block in dnode2, we will get wrong extent_info data:
>>>>>> map->m_len = 1
>>>>>> ofs = start_pgofs - map->m_lblk = 1882 - 1881 = 1
>>>>>>
>>>>>> ei.fofs = start_pgofs = 1882
>>>>>> ei.len = map->m_len - ofs = 1 - 1 = 0
>>>>>>
>>>>>> Fix it by skipping updating this kind of extent info.
>>>>>>
>>>>>> Signed-off-by: wangzijie <wangzijie1@...or.com>
>>>>>> ---
>>>>>> fs/f2fs/data.c | 3 +++
>>>>>> 1 file changed, 3 insertions(+)
>>>>>>
>>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>>> index 7961e0ddf..b8bb71852 100644
>>>>>> --- a/fs/f2fs/data.c
>>>>>> +++ b/fs/f2fs/data.c
>>>>>> @@ -1649,6 +1649,9 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>>>>>>
>>>>>> switch (flag) {
>>>>>> case F2FS_GET_BLOCK_PRECACHE:
>>>>>> + if (__is_valid_data_blkaddr(map->m_pblk) &&
>>>>>> + start_pgofs - map->m_lblk == map->m_len)
>>>>>> + map->m_flags &= ~F2FS_MAP_MAPPED;
>>>>>
>>>>> It looks we missed to reset value for map variable in f2fs_precache_extents(),
>>>>> what do you think of this?
>>>>>
>>>>> ---
>>>>> fs/f2fs/file.c | 4 +++-
>>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>> index 1aae4361d0a8..2b14151d4130 100644
>>>>> --- a/fs/f2fs/file.c
>>>>> +++ b/fs/f2fs/file.c
>>>>> @@ -3599,7 +3599,7 @@ static int f2fs_ioc_io_prio(struct file *filp, unsigned long arg)
>>>>> int f2fs_precache_extents(struct inode *inode)
>>>>> {
>>>>> struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>> - struct f2fs_map_blocks map;
>>>>> + struct f2fs_map_blocks map = { 0 };
>>>>> pgoff_t m_next_extent;
>>>>> loff_t end;
>>>>> int err;
>>>>> @@ -3617,6 +3617,8 @@ int f2fs_precache_extents(struct inode *inode)
>>>>>
>>>>> while (map.m_lblk < end) {
>>>>> map.m_len = end - map.m_lblk;
>>>>> + map.m_pblk = 0;
>>>>> + map.m_flags = 0;
>>>>>
>>>>> f2fs_down_write(&fi->i_gc_rwsem[WRITE]);
>>>>> err = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_PRECACHE);
>>>>> --
>>>>> 2.49.0
>>>>>
>>>>> Thanks,
>>>>>
>>>>>> goto sync_out;
>>>>>> case F2FS_GET_BLOCK_BMAP:
>>>>>> map->m_pblk = 0;
>>>>
>>>>
>>>> We have already reset m_flags (map->m_flags = 0) in f2fs_map_blocks().
>>>
>>> Zijie:
>>>
>>> Oops, that's right, thanks for correcting me.
>>>
>>>>
>>>> I think that this bug is caused by we missed to reset m_flags when we
>>>> goto next_dnode in below caseļ¼
>>>>
>>>> Data layout is something like this:
>>>> dnode1: dnode2:
>>>> [0] A [0] NEW_ADDR
>>>> [1] A+1 [1] 0x0
>>>> ...
>>>> [1016] A+1016
>>>> [1017] B (B!=A+1017) [1017] 0x0
>>>>
>>>> we map the last block(valid blkaddr) in dnode1:
>>>> map->m_flags |= F2FS_MAP_MAPPED;
>>>> map->m_pblk = blkaddr(valid blkaddr);
>>>> map->m_len = 1;
>>>> then we goto next_dnode, meet the first block in dnode2(hole), goto sync_out:
>>>> map->m_flags & F2FS_MAP_MAPPED == true, and we make wrong blkaddr/len for extent_info.
>>>
>>> So, can you please add above explanation into commit message? that
>>> should be helpful for understanding the problem more clearly.
>>>
>>> Please take a look at this case w/ your patch:
>>>
>>> mkfs.f2fs -O extra_attr,compression /dev/vdb -f
>>> mount /dev/vdb /mnt/f2fs -o mode=lfs
>>> cd /mnt/f2fs
>>> f2fs_io write 1 0 1883 rand dsync testfile
>>> f2fs_io fallocate 0 7712768 4096 testfile
>>> f2fs_io write 1 1881 1 rand buffered testfile
>>> xfs_io testfile -c "fsync"
>>> cd /
>>> umount /mnt/f2fs
>>> mount /dev/vdb /mnt/f2fs
>>> f2fs_io precache_extents /mnt/f2fs/testfile
>>> umount /mnt/f2fs
>>>
>>> f2fs_io-733 [010] ..... 78.134136: f2fs_update_read_extent_tree_range: dev = (253,16), ino = 4, pgofs = 1882, len = 0, blkaddr = 17410, c_len = 0
>>>
>>> I suspect we need this?
>>>
>>> @@ -1784,7 +1781,8 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>>> }
>>>
>>> if (flag == F2FS_GET_BLOCK_PRECACHE) {
>>> - if (map->m_flags & F2FS_MAP_MAPPED) {
>>> + if ((map->m_flags & F2FS_MAP_MAPPED) &&
>>> + (map->m_len - ofs)) {
>>> unsigned int ofs = start_pgofs - map->m_lblk;
>>>
>>> f2fs_update_read_extent_cache_range(&dn,
>>
>> Thanks for pointing out this. Let me find a way to cover these cases and do more test.
>>
>>> BTW, I find another bug, if one blkaddr is adjcent to previous extent,
>>> but and it is valid, we need to set m_next_extent to pgofs rather than
>>> pgofs + 1.
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index cbf8841642c7..ac88ed68059c 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -1789,8 +1789,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>>> start_pgofs, map->m_pblk + ofs,
>>> map->m_len - ofs);
>>> }
>>> - if (map->m_next_extent)
>>> - *map->m_next_extent = pgofs + 1;
>>> + if (map->m_next_extent) {
>>> + *map->m_next_extent = pgofs;
>>> + if (!__is_valid_data_blkaddr(blkaddr))
>>> + *map->m_next_extent += 1;
>>> + }
>>> }
>>> f2fs_put_dnode(&dn);
>>
>> Maybe it can be this?
>> if (map->m_next_extent)
>> *map->m_next_extent = is_hole ? pgofs + 1 : pgofs;
>
>It's better, will update, thank you. :)
>
>Thanks,
Hi Chao,
I test some cases with this change:
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 7961e0ddf..7093fdc95 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1777,13 +1777,13 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
if (flag == F2FS_GET_BLOCK_PRECACHE) {
if (map->m_flags & F2FS_MAP_MAPPED) {
unsigned int ofs = start_pgofs - map->m_lblk;
-
- f2fs_update_read_extent_cache_range(&dn,
- start_pgofs, map->m_pblk + ofs,
- map->m_len - ofs);
+ if (map->m_len - ofs > 0)
+ f2fs_update_read_extent_cache_range(&dn,
+ start_pgofs, map->m_pblk + ofs,
+ map->m_len - ofs);
}
if (map->m_next_extent)
- *map->m_next_extent = pgofs + 1;
+ *map->m_next_extent = is_hole ? pgofs + 1 : pgofs;
}
f2fs_put_dnode(&dn);
unlock_out:
test cases:
case1:
dnode1: dnode2:
[0] A [0] NEW_ADDR
[1] A+1 [1] 0x0
... ....
[1016] A+1016
[1017] B (B!=A+1017) [1017] 0x0
case2:
dnode1: dnode2:
[0] A [0] C (C!=B+1)
[1] A+1 [1] C+1
... ....
[1016] A+1016
[1017] B (B!=A+1017) [1017] 0x0
case3:
dnode1: dnode2:
[0] A [0] C (C!=B+2)
[1] A+1 [1] C+1
... ....
[1015] A+1015
[1016] B (B!=A+1016)
[1017] B+1 [1017] 0x0
case4:
one blkaddr is adjcent to previous extent, and it is valid.
And from the result, it seems this change can cover these
situations correctly.
Do we need a patch with this change?
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