From: Yongpeng Yang Date: Mon, 23 Mar 2026 12:06:24 +0000 (+0800) Subject: f2fs: fix fiemap boundary handling when read extent cache is incomplete X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=95e159ad3e52f7478cfd22e44ec37c9f334f8993;p=thirdparty%2Fkernel%2Fstable.git f2fs: fix fiemap boundary handling when read extent cache is incomplete f2fs_fiemap() calls f2fs_map_blocks() to obtain the block mapping a file, and then merges contiguous mappings into extents. If the mapping is found in the read extent cache, node blocks do not need to be read. However, in the following scenario, a contiguous extent can be split into two extents: $ dd if=/dev/zero of=data.128M bs=1M count=128 $ losetup -f data.128M $ mkfs.f2fs /dev/loop0 -f $ mount -o mode=lfs /dev/loop0 /mnt/f2fs/ $ cd /mnt/f2fs/ $ dd if=/dev/zero of=data.72M bs=1M count=72 && sync $ dd if=/dev/zero of=data.4M bs=1M count=4 && sync $ dd if=/dev/zero of=data.4M bs=1M count=2 seek=2 conv=notrunc && sync $ echo 3 > /proc/sys/vm/drop_caches $ dd if=/dev/zero of=data.4M bs=1M count=2 seek=0 conv=notrunc && sync $ dd if=/dev/zero of=data.4M bs=1M count=2 seek=0 conv=notrunc && sync $ f2fs_io fiemap 0 1024 data.4M Fiemap: offset = 0 len = 1024 logical addr. physical addr. length flags 0 0000000000000000 0000000006400000 0000000000200000 00001000 1 0000000000200000 0000000006600000 0000000000200000 00001001 Although the physical addresses of the ranges 0～2MB and 2M～4MB are contiguous, the mapping for the 2M～4MB range is not present in memory. When the physical addresses for the 0～2MB range are updated, no merge happens because the adjacent mapping is missing from the in-memory cache. As a result, fiemap reports two separate extents instead of a single contiguous one. The root cause is that the read extent cache does not guarantee that all blocks of an extent are present in memory. Therefore, when the extent length returned by f2fs_map_blocks_cached() is smaller than maxblocks, the remaining mappings are retrieved via f2fs_get_dnode_of_data() to ensure correct fiemap extent boundary handling. Cc: stable@kernel.org Fixes: cd8fc5226bef ("f2fs: remove the create argument to f2fs_map_blocks") Signed-off-by: Yongpeng Yang Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim --- diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index a690442b7440..0e108c701aa3 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -1636,8 +1636,26 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag) lfs_dio_write = (flag == F2FS_GET_BLOCK_DIO && f2fs_lfs_mode(sbi) && map->m_may_create); - if (!map->m_may_create && f2fs_map_blocks_cached(inode, map, flag)) - goto out; + if (!map->m_may_create && f2fs_map_blocks_cached(inode, map, flag)) { + struct extent_info ei; + + /* + * 1. If map->m_multidev_dio is true, map->m_pblk cannot be + * waitted by f2fs_wait_on_block_writeback_range() and are not + * mergeable. + * 2. If pgofs hits the read extent cache, it means the mapping + * is already cached in the extent cache, but it is not + * mergeable, and there is no need to query the mapping again + * via f2fs_get_dnode_of_data(). + */ + pgofs = (pgoff_t)map->m_lblk + map->m_len; + if (map->m_len == maxblocks || + map->m_multidev_dio || + f2fs_lookup_read_extent_cache(inode, pgofs, &ei)) + goto out; + ofs = map->m_len; + goto map_more; + } map->m_bdev = inode->i_sb->s_bdev; map->m_multidev_dio = @@ -1648,7 +1666,8 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag) /* it only supports block size == page size */ pgofs = (pgoff_t)map->m_lblk; - end = pgofs + maxblocks; +map_more: + end = (pgoff_t)map->m_lblk + maxblocks; if (flag == F2FS_GET_BLOCK_PRECACHE) mode = LOOKUP_NODE_RA;