GFS2: Cache the most recently used resource group in the inode

This means that after the initial allocation for any inode, the
last used resource group is cached in the inode for future use.
This drastically reduces the number of lookups of resource
groups in the common case, and this the contention on that
data structure.

The allocation algorithm is the same as previously, except that we
always check to see if the goal block is within the cached rgrp
first before going to the rbtree to look one up.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 25 insertions, 26 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 88d5b75067a8..5bfb97002c2a 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -882,24 +882,21 @@ struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip)
 /**
  * try_rgrp_fit - See if a given reservation will fit in a given RG
  * @rgd: the RG data
- * @al: the struct gfs2_alloc structure describing the reservation
+ * @ip: the inode
  *
  * If there's room for the requested blocks to be allocated from the RG:
- *   Sets the $al_rgd field in @al.
  *
  * Returns: 1 on success (it fits), 0 on failure (it doesn't fit)
  */
 
-static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
+static int try_rgrp_fit(const struct gfs2_rgrpd *rgd, const struct gfs2_inode *ip)
 {
+        const struct gfs2_alloc *al = ip->i_alloc;
+
         if (rgd->rd_flags & (GFS2_RGF_NOALLOC | GFS2_RDF_ERROR))
                 return 0;
-
-        if (rgd->rd_free_clone >= al->al_requested) {
-                al->al_rgd = rgd;
+        if (rgd->rd_free_clone >= al->al_requested)
                 return 1;
-        }
-
         return 0;
 }
 
@@ -985,7 +982,10 @@ static int get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
         int error, rg_locked;
         int loops = 0;
 
-        rgd = begin = gfs2_blk2rgrpd(sdp, ip->i_goal);
+        if (ip->i_rgd && rgrp_contains_block(ip->i_rgd, ip->i_goal))
+                rgd = begin = ip->i_rgd;
+        else
+                rgd = begin = gfs2_blk2rgrpd(sdp, ip->i_goal);
 
         if (rgd == NULL)
                 return -EBADSLT;
@@ -1002,8 +1002,10 @@ static int get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
                 }
                 switch (error) {
                 case 0:
-                        if (try_rgrp_fit(rgd, al))
+                        if (try_rgrp_fit(rgd, ip)) {
+                                ip->i_rgd = rgd;
                                 return 0;
+                        }
                         if (rgd->rd_flags & GFS2_RDF_CHECK)
                                 try_rgrp_unlink(rgd, last_unlinked, ip->i_no_addr);
                         if (!rg_locked)
@@ -1014,7 +1016,6 @@ static int get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
                         if (rgd == begin)
                                 loops++;
                         break;
-
                 default:
                         return error;
                 }
@@ -1042,21 +1043,20 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip,
         if (gfs2_assert_warn(sdp, al->al_requested))
                 return -EINVAL;
 
-try_again:
         do {
                 error = get_local_rgrp(ip, &last_unlinked);
-                /* If there is no space, flushing the log may release some */
-                if (error) {
-                        if (ip == GFS2_I(sdp->sd_rindex) &&
-                            !sdp->sd_rindex_uptodate) {
-                                error = gfs2_ri_update(ip);
-                                if (error)
-                                        return error;
-                                goto try_again;
-                        }
-                        gfs2_log_flush(sdp, NULL);
+                if (error != -ENOSPC)
+                        break;
+                /* Check that fs hasn't grown if writing to rindex */
+                if (ip == GFS2_I(sdp->sd_rindex) && !sdp->sd_rindex_uptodate) {
+                        error = gfs2_ri_update(ip);
+                        if (error)
+                                break;
+                        continue;
                 }
-        } while (error && tries++ < 3);
+                /* Flushing the log may release space */
+                gfs2_log_flush(sdp, NULL);
+        } while (tries++ < 3);
 
         if (error)
                 return error;
@@ -1086,7 +1086,6 @@ void gfs2_inplace_release(struct gfs2_inode *ip)
                              al->al_alloced, al->al_requested, al->al_file,
                              al->al_line);
 
-        al->al_rgd = NULL;
         if (al->al_rgd_gh.gh_gl)
                 gfs2_glock_dq_uninit(&al->al_rgd_gh);
 }
@@ -1339,7 +1338,7 @@ int gfs2_alloc_block(struct gfs2_inode *ip, u64 *bn, unsigned int *n)
         if (al == NULL)
                 return -ECANCELED;
 
-        rgd = al->al_rgd;
+        rgd = ip->i_rgd;
 
         if (rgrp_contains_block(rgd, ip->i_goal))
                 goal = ip->i_goal - rgd->rd_data0;
@@ -1398,7 +1397,7 @@ int gfs2_alloc_di(struct gfs2_inode *dip, u64 *bn, u64 *generation)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
         struct gfs2_alloc *al = dip->i_alloc;
-        struct gfs2_rgrpd *rgd = al->al_rgd;
+        struct gfs2_rgrpd *rgd = dip->i_rgd;
         u32 blk;
         u64 block;
         unsigned int n = 1;