On 02/03, Yongpeng Yang wrote: > From: Yongpeng Yang <[email protected]> > > 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: > > root@vm:/mnt/f2fs# dd if=/dev/zero of=data.4M bs=1M count=4 && sync > root@vm:/mnt/f2fs# dd if=/dev/zero of=data.4M bs=1M count=2 seek=2 > conv=notrunc && sync > root@vm:/mnt/f2fs# echo 3 > /proc/sys/vm/drop_caches # drop 2M~4M extent cache > root@vm:/mnt/f2fs# dd if=/dev/zero of=data.4M bs=1M count=2 seek=0 > conv=notrunc && sync > root@vm:/mnt/f2fs# 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. > > Fixes: cd8fc5226bef ("f2fs: remove the create argument to f2fs_map_blocks") > Signed-off-by: Yongpeng Yang <[email protected]> > --- > fs/f2fs/data.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index 42f15fd9c68e..eedadccf86bb 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -1623,8 +1623,18 @@ 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) { > + if (f2fs_map_blocks_cached(inode, map, flag)) { > + if (map->m_len == maxblocks) > + goto out; > + else { > + pgofs = (pgoff_t)map->m_lblk + map->m_len; > + end = map->m_lblk + maxblocks; > + ofs = map->m_len; > + goto next_dnode; > + } > + } > + }
This patch makes a system panic. > > map->m_bdev = inode->i_sb->s_bdev; > map->m_multidev_dio = > -- > 2.43.0 _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
