[f2fs-dev] [PATCH v3 1/2] f2fs: fix zero-sized extent for precache extents

[f2fs-dev] [PATCH v3 1/2] f2fs: fix zero-sized extent for precache extents

[wangzijie]

Script to reproduce:
f2fs_io write 1 0 1881 rand dsync testfile
f2fs_io fallocate 0 7708672 4096 testfile
f2fs_io write 1 1881 1 rand buffered testfile
fsync testfile
umount
mount
f2fs_io precache_extents testfile

When the 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

During precache_extents, 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 zero-sized extent:

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


Rebased on patch[1], this patch can cover these cases to avoid zero-sized extent:
A,B,C is valid blkaddr
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

[1] https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/

Fixes: c4020b2da4c9 ("f2fs: support F2FS_IOC_PRECACHE_EXTENTS")
Signed-off-by: wangzijie <wangzijie1@honor.com>
---
Rebased on:
https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/
v2:
https://lore.kernel.org/linux-f2fs-devel/20250915035246.98055-1-wangzijie1@honor.com/
---
 fs/f2fs/data.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 838eae39d..7a5170b32 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1778,9 +1778,10 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
 		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 = is_hole ? pgofs + 1 : pgofs;
-- 
2.25.1



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[f2fs-dev] [PATCH v3 2/2] f2fs: fix infinite loop in __insert_extent_tree()

[wangzijie]

When we get wrong extent info data, and look up extent_node in rb tree,
it will cause infinite loop (CONFIG_F2FS_CHECK_FS=n). Avoiding this by
return NULL and print some kernel messages in that case.

Signed-off-by: wangzijie <wangzijie1@honor.com>
---
v3:
- followed by Jaegeuk's suggestion to print some kernel messages 
---
 fs/f2fs/extent_cache.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 199c1e7a8..ba0a07bfd 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -604,7 +604,13 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
 			p = &(*p)->rb_right;
 			leftmost = false;
 		} else {
+			f2fs_err_ratelimited(sbi, "%s: corrupted extent, type: %d, "
+				"extent node in rb tree [%u, %u, %u], age [%llu, %llu], "
+				"extent node to insert [%u, %u, %u], age [%llu, %llu]",
+				__func__, et->type, en->ei.fofs, en->ei.blk, en->ei.len, en->ei.age,
+				en->ei.last_blocks, ei->fofs, ei->blk, ei->len, ei->age, ei->last_blocks);
 			f2fs_bug_on(sbi, 1);
+			return NULL;
 		}
 	}
 
-- 
2.25.1



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Re: [f2fs-dev] [PATCH v3 1/2] f2fs: fix zero-sized extent for precache extents

[Chao Yu via Linux-f2fs-devel]

On 9/17/25 10:36, wangzijie wrote:
> Script to reproduce:
> f2fs_io write 1 0 1881 rand dsync testfile
> f2fs_io fallocate 0 7708672 4096 testfile
> f2fs_io write 1 1881 1 rand buffered testfile
> fsync testfile
> umount
> mount
> f2fs_io precache_extents testfile
> 
> When the 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
> 
> During precache_extents, 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 zero-sized extent:
> 
> 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
> 
> 
> Rebased on patch[1], this patch can cover these cases to avoid zero-sized extent:
> A,B,C is valid blkaddr
> 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
> 
> [1] https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/
> 
> Fixes: c4020b2da4c9 ("f2fs: support F2FS_IOC_PRECACHE_EXTENTS")
> Signed-off-by: wangzijie <wangzijie1@honor.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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Re: [f2fs-dev] [PATCH v3 2/2] f2fs: fix infinite loop in __insert_extent_tree()

[Chao Yu via Linux-f2fs-devel]

On 9/17/25 10:36, wangzijie wrote:
> When we get wrong extent info data, and look up extent_node in rb tree,
> it will cause infinite loop (CONFIG_F2FS_CHECK_FS=n). Avoiding this by
> return NULL and print some kernel messages in that case.
> 
> Signed-off-by: wangzijie <wangzijie1@honor.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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Re: [f2fs-dev] [PATCH v3 1/2] f2fs: fix zero-sized extent for precache extents

[Jaegeuk Kim via Linux-f2fs-devel]

On 09/17, wangzijie wrote:
> Script to reproduce:
> f2fs_io write 1 0 1881 rand dsync testfile
> f2fs_io fallocate 0 7708672 4096 testfile
> f2fs_io write 1 1881 1 rand buffered testfile
> fsync testfile
> umount
> mount
> f2fs_io precache_extents testfile
> 
> When the 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
> 
> During precache_extents, 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 zero-sized extent:
> 
> 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
> 
> 
> Rebased on patch[1], this patch can cover these cases to avoid zero-sized extent:
> A,B,C is valid blkaddr
> 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
> 
> [1] https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/
> 
> Fixes: c4020b2da4c9 ("f2fs: support F2FS_IOC_PRECACHE_EXTENTS")
> Signed-off-by: wangzijie <wangzijie1@honor.com>
> ---
> Rebased on:
> https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/
> v2:
> https://lore.kernel.org/linux-f2fs-devel/20250915035246.98055-1-wangzijie1@honor.com/
> ---
>  fs/f2fs/data.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 838eae39d..7a5170b32 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1778,9 +1778,10 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>  		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)

Applied with
			if (map->m_len > ofs)

> +				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 = is_hole ? pgofs + 1 : pgofs;
> -- 
> 2.25.1


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Re: [f2fs-dev] [PATCH v3 1/2] f2fs: fix zero-sized extent for precache extents

[patchwork-bot+f2fs--- via Linux-f2fs-devel]

Hello:

This series was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Wed, 17 Sep 2025 10:36:21 +0800 you wrote:
> Script to reproduce:
> f2fs_io write 1 0 1881 rand dsync testfile
> f2fs_io fallocate 0 7708672 4096 testfile
> f2fs_io write 1 1881 1 rand buffered testfile
> fsync testfile
> umount
> mount
> f2fs_io precache_extents testfile
> 
> [...]

Here is the summary with links:
  - [f2fs-dev,v3,1/2] f2fs: fix zero-sized extent for precache extents
    (no matching commit)
  - [f2fs-dev,v3,2/2] f2fs: fix infinite loop in __insert_extent_tree()
    https://git.kernel.org/jaegeuk/f2fs/c/23361bd54966

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html




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