From: Darrick J. Wong darrick.wong@oracle.com
[ Upstream commit d88850bd5516a77c6f727e8b6cefb64e0cc929c7 ]
Fix some off-by-one errors in xfs_rtalloc_query_range. The highest key in the realtime bitmap is always one less than the number of rt extents, which means that the key clamp at the start of the function is wrong. The 4th argument to xfs_rtfind_forw is the highest rt extent that we want to probe, which means that passing 1 less than the high key is wrong. Finally, drop the rem variable that controls the loop because we can compare the iteration point (rtstart) against the high key directly.
The sordid history of this function is that the original commit (fb3c3) incorrectly passed (high_rec->ar_startblock - 1) as the 'limit' parameter to xfs_rtfind_forw. This was wrong because the "high key" is supposed to be the largest key for which the caller wants result rows, not the key for the first row that could possibly be outside the range that the caller wants to see.
A subsequent attempt (8ad56) to strengthen the parameter checking added incorrect clamping of the parameters to the number of rt blocks in the system (despite the bitmap functions all taking units of rt extents) to avoid querying ranges past the end of rt bitmap file but failed to fix the incorrect _rtfind_forw parameter. The original _rtfind_forw parameter error then survived the conversion of the startblock and blockcount fields to rt extents (a0e5c), and the most recent off-by-one fix (a3a37) thought it was patching a problem when the end of the rt volume is not in use, but none of these fixes actually solved the original problem that the author was confused about the "limit" argument to xfs_rtfind_forw.
Sadly, all four of these patches were written by this author and even his own usage of this function and rt testing were inadequate to get this fixed quickly.
Original-problem: fb3c3de2f65c ("xfs: add a couple of queries to iterate free extents in the rtbitmap") Not-fixed-by: 8ad560d2565e ("xfs: strengthen rtalloc query range checks") Not-fixed-by: a0e5c435babd ("xfs: fix xfs_rtalloc_rec units") Fixes: a3a374bf1889 ("xfs: fix off-by-one error in xfs_rtalloc_query_range") Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Chandan Babu R chandanrlinux@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/xfs/libxfs/xfs_rtbitmap.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c index 9498ced947be9..2a38576189307 100644 --- a/fs/xfs/libxfs/xfs_rtbitmap.c +++ b/fs/xfs/libxfs/xfs_rtbitmap.c @@ -1018,7 +1018,6 @@ xfs_rtalloc_query_range( struct xfs_mount *mp = tp->t_mountp; xfs_rtblock_t rtstart; xfs_rtblock_t rtend; - xfs_rtblock_t rem; int is_free; int error = 0;
@@ -1027,13 +1026,12 @@ xfs_rtalloc_query_range( if (low_rec->ar_startext >= mp->m_sb.sb_rextents || low_rec->ar_startext == high_rec->ar_startext) return 0; - if (high_rec->ar_startext > mp->m_sb.sb_rextents) - high_rec->ar_startext = mp->m_sb.sb_rextents; + high_rec->ar_startext = min(high_rec->ar_startext, + mp->m_sb.sb_rextents - 1);
/* Iterate the bitmap, looking for discrepancies. */ rtstart = low_rec->ar_startext; - rem = high_rec->ar_startext - rtstart; - while (rem) { + while (rtstart <= high_rec->ar_startext) { /* Is the first block free? */ error = xfs_rtcheck_range(mp, tp, rtstart, 1, 1, &rtend, &is_free); @@ -1042,7 +1040,7 @@ xfs_rtalloc_query_range(
/* How long does the extent go for? */ error = xfs_rtfind_forw(mp, tp, rtstart, - high_rec->ar_startext - 1, &rtend); + high_rec->ar_startext, &rtend); if (error) break;
@@ -1055,7 +1053,6 @@ xfs_rtalloc_query_range( break; }
- rem -= rtend - rtstart + 1; rtstart = rtend + 1; }