GFS2: Don't brelse rgrp buffer_heads every allocation

This patch allows the block allocation code to retain the buffers
for the resource groups so they don't need to be re-read from buffer
cache with every request. This is a performance improvement that's
especially noticeable when resource groups are very large. For
example, with 2GB resource groups and 4K blocks, there can be 33
blocks for every resource group. This patch allows those 33 buffers
to be kept around and not read in and thrown away with every
operation. The buffers are released when the resource group is
either synced or invalidated.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 1249b2bb2830..fa3fa5e94553 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -144,6 +144,12 @@ static void rgrp_go_sync(struct gfs2_glock *gl)
         struct gfs2_rgrpd *rgd;
         int error;
 
+        spin_lock(&gl->gl_spin);
+        rgd = gl->gl_object;
+        if (rgd)
+                gfs2_rgrp_brelse(rgd);
+        spin_unlock(&gl->gl_spin);
+
         if (!test_and_clear_bit(GLF_DIRTY, &gl->gl_flags))
                 return;
         GLOCK_BUG_ON(gl, gl->gl_state != LM_ST_EXCLUSIVE);
@@ -175,15 +181,17 @@ static void rgrp_go_inval(struct gfs2_glock *gl, int flags)
 {
         struct gfs2_sbd *sdp = gl->gl_sbd;
         struct address_space *mapping = &sdp->sd_aspace;
+        struct gfs2_rgrpd *rgd = gl->gl_object;
+
+        if (rgd)
+                gfs2_rgrp_brelse(rgd);
 
         WARN_ON_ONCE(!(flags & DIO_METADATA));
         gfs2_assert_withdraw(sdp, !atomic_read(&gl->gl_ail_count));
         truncate_inode_pages_range(mapping, gl->gl_vm.start, gl->gl_vm.end);
 
-        if (gl->gl_object) {
-                struct gfs2_rgrpd *rgd = (struct gfs2_rgrpd *)gl->gl_object;
+        if (rgd)
                 rgd->rd_flags &= ~GFS2_RDF_UPTODATE;
-        }
 }
 
 /**