Commit 4a495624 authored Jun 23, 2017 by Darrick J. Wong Committed by Theodore Ts'o Jun 23, 2017

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: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore 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;

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