xfs: make xfs_rtalloc_query_range input parameters const

In commit 8ad560d2565e, we changed xfs_rtalloc_query_range to constrain
the range of bits in the realtime bitmap file that would actually be
searched.  In commit a3a374bf1889, we changed the range again
(incorrectly), leading to the fix in commit d88850bd5516, which finally
corrected the range check code.  Unfortunately, the author never noticed
that the function modifies its input parameters, which is a totaly no-no
since none of the other range query functions change their input
parameters.

So, fix this function yet again to stash the upper end of the query
range (i.e. the high key) in a local variable and hope this is the last
time I have to fix my own function.  While we're at it, mark the key
inputs const so nobody makes this mistake again. :(

Fixes: 8ad560d2565e ("xfs: strengthen rtalloc query range checks")
Not-fixed-by: a3a374bf1889 ("xfs: fix off-by-one error in xfs_rtalloc_query_range")
Not-fixed-by: d88850bd5516 ("xfs: fix high key handling in the rt allocator's query_range function")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 483375c6a735acddaf4dff957f3604b8e2507d35..5740ba664867680bf258f75397e5bd11aae0f28c 100644 (file)
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -1009,8 +1009,8 @@ xfs_rtfree_extent(
 int
 xfs_rtalloc_query_range(
        struct xfs_trans                *tp,
-       struct xfs_rtalloc_rec          *low_rec,
-       struct xfs_rtalloc_rec          *high_rec,
+       const struct xfs_rtalloc_rec    *low_rec,
+       const struct xfs_rtalloc_rec    *high_rec,
        xfs_rtalloc_query_range_fn      fn,
        void                            *priv)
 {
@@ -1018,6 +1018,7 @@ xfs_rtalloc_query_range(
        struct xfs_mount                *mp = tp->t_mountp;
        xfs_rtblock_t                   rtstart;
        xfs_rtblock_t                   rtend;
+       xfs_rtblock_t                   high_key;
        int                             is_free;
        int                             error = 0;
 
@@ -1026,12 +1027,12 @@ xfs_rtalloc_query_range(
        if (low_rec->ar_startext >= mp->m_sb.sb_rextents ||
            low_rec->ar_startext == high_rec->ar_startext)
                return 0;
-       high_rec->ar_startext = min(high_rec->ar_startext,
-                       mp->m_sb.sb_rextents - 1);
+
+       high_key = min(high_rec->ar_startext, mp->m_sb.sb_rextents - 1);
 
        /* Iterate the bitmap, looking for discrepancies. */
        rtstart = low_rec->ar_startext;
-       while (rtstart <= high_rec->ar_startext) {
+       while (rtstart <= high_key) {
                /* Is the first block free? */
                error = xfs_rtcheck_range(mp, tp, rtstart, 1, 1, &rtend,
                                &is_free);
@@ -1039,8 +1040,7 @@ xfs_rtalloc_query_range(
                        break;
 
                /* How long does the extent go for? */
-               error = xfs_rtfind_forw(mp, tp, rtstart,
-                               high_rec->ar_startext, &rtend);
+               error = xfs_rtfind_forw(mp, tp, rtstart, high_key, &rtend);
                if (error)
                        break;
 

diff --git a/fs/xfs/xfs_rtalloc.h b/fs/xfs/xfs_rtalloc.h
index ed885620589c4236b0a1300db263b74c7a9ce8e7..51097cb24311dd71ca2c782e3d5ca5944196282f 100644 (file)
--- a/fs/xfs/xfs_rtalloc.h
+++ b/fs/xfs/xfs_rtalloc.h
@@ -124,10 +124,9 @@ int xfs_rtfree_range(struct xfs_mount *mp, struct xfs_trans *tp,
                     xfs_rtblock_t start, xfs_extlen_t len,
                     struct xfs_buf **rbpp, xfs_fsblock_t *rsb);
 int xfs_rtalloc_query_range(struct xfs_trans *tp,
-                           struct xfs_rtalloc_rec *low_rec,
-                           struct xfs_rtalloc_rec *high_rec,
-                           xfs_rtalloc_query_range_fn fn,
-                           void *priv);
+               const struct xfs_rtalloc_rec *low_rec,
+               const struct xfs_rtalloc_rec *high_rec,
+               xfs_rtalloc_query_range_fn fn, void *priv);
 int xfs_rtalloc_query_all(struct xfs_trans *tp,
                          xfs_rtalloc_query_range_fn fn,
                          void *priv);