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Message-ID: <6464ded0-b25e-4ce8-a05b-6caa394fbe63@kernel.org>
Date: Fri, 12 Sep 2025 18:38:58 +0800
From: Chao Yu <chao@...nel.org>
To: wangzijie <wangzijie1@...or.com>
Cc: chao@...nel.org, feng.han@...or.com, jaegeuk@...nel.org,
linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: fix wrong extent_info data for
precache extents
On 9/12/2025 6:06 PM, wangzijie wrote:
>> 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?
Zijie, thanks for the test.
IMO, we'd better use these changes:
-
- 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);
instead of
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;
Can you please rebase your patchset on mine and send v2?
https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org
BTW, please add fixes line in your patch.
Thanks,
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