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Commit 4a495624 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Theodore Ts'o
Browse files

ext4: fix off-by-one fsmap error on 1k block filesystems 



For 1k-block filesystems, the filesystem starts at block 1, not block 0.
This fact is recorded in s_first_data_block, so use that to bump up the
start_fsb before we start querying the filesystem for its space map.
Without this, ext4/026 fails on 1k block ext4 because various functions
(notably ext4_get_group_no_and_offset) don't know what to do with an
fsblock that is "before" the start of the filesystem and return garbage
results (blockgroup 2^32-1, etc.) that confuse fsmap.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent bdddf342

fs/ext4/fsmap.c

+4 −0
Original line number Diff line number Diff line
@@ -480,6 +480,7 @@ static int ext4_getfsmap_datadev(struct super_block *sb, 
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	ext4_fsblk_t start_fsb;

	ext4_fsblk_t end_fsb;

	ext4_fsblk_t bofs;

	ext4_fsblk_t eofs;

	ext4_group_t start_ag;

	ext4_group_t end_ag;
@@ -487,9 +488,12 @@ static int ext4_getfsmap_datadev(struct super_block *sb, 
	ext4_grpblk_t last_cluster;

	int error = 0;



	bofs = le32_to_cpu(sbi->s_es->s_first_data_block);

	eofs = ext4_blocks_count(sbi->s_es);

	if (keys[0].fmr_physical >= eofs)

		return 0;

	else if (keys[0].fmr_physical < bofs)

		keys[0].fmr_physical = bofs;

	if (keys[1].fmr_physical >= eofs)

		keys[1].fmr_physical = eofs - 1;

	start_fsb = keys[0].fmr_physical;