xfs: invert the realtime summary cache

Source kernel commit: e23aaf450de733044a74bc95528f728478b61c2a

In commit 355e3532132b ("xfs: cache minimum realtime summary level"), I
added a cache of the minimum level of the realtime summary that has any
free extents. However, it turns out that the _maximum_ level is more
useful for upcoming optimizations, and basically equivalent for the
existing usage. So, let's change the meaning of the cache to be the
maximum level + 1, or 0 if there are no free extents.

For example, if the cache contains:

{0, 4}

then there are no free extents starting in realtime bitmap block 0, and
there are no free extents larger than or equal to 2^4 blocks starting in
realtime bitmap block 1. The cache is a loose upper bound, so there may
or may not be free extents smaller than 2^4 blocks in realtime bitmap
block 1.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/libxfs/xfs_rtbitmap.c b/libxfs/xfs_rtbitmap.c
index f5d7e14abf91206b715f03fbee5c536fd59e1a18..8f313339e97f1803d5df9fdbd97741308dee1f47 100644 (file)
--- a/libxfs/xfs_rtbitmap.c
+++ b/libxfs/xfs_rtbitmap.c
@@ -493,10 +493,10 @@ xfs_rtmodify_summary_int(
                xfs_suminfo_t   val = xfs_suminfo_add(args, infoword, delta);
 
                if (mp->m_rsum_cache) {
-                       if (val == 0 && log == mp->m_rsum_cache[bbno])
-                               mp->m_rsum_cache[bbno]++;
-                       if (val != 0 && log < mp->m_rsum_cache[bbno])
+                       if (val == 0 && log + 1 == mp->m_rsum_cache[bbno])
                                mp->m_rsum_cache[bbno] = log;
+                       if (val != 0 && log >= mp->m_rsum_cache[bbno])
+                               mp->m_rsum_cache[bbno] = log + 1;
                }
                xfs_trans_log_rtsummary(args, infoword);
                if (sum)