GFS2: Reduce file fragmentation

This patch reduces GFS2 file fragmentation by pre-reserving blocks. The
resulting improved on disk layout greatly speeds up operations in cases
which would have resulted in interlaced allocation of blocks previously.
A typical example of this is 10 parallel dd processes, each writing to a
file in a common dirctory.

The implementation uses an rbtree of reservations attached to each
resource group (and each inode).

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

1 files changed, 28 insertions, 9 deletions

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 2b035e0959b2..c53c67e30bd4 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -521,6 +521,9 @@ static int make_dinode(struct gfs2_inode *dip, struct gfs2_glock *gl,
         int error;
 
         munge_mode_uid_gid(dip, &mode, &uid, &gid);
+        error = gfs2_rindex_update(sdp);
+        if (error)
+                return error;
 
         error = gfs2_quota_lock(dip, uid, gid);
         if (error)
@@ -551,6 +554,10 @@ static int link_dinode(struct gfs2_inode *dip, const struct qstr *name,
         struct buffer_head *dibh;
         int error;
 
+        error = gfs2_rindex_update(sdp);
+        if (error)
+                return error;
+
         error = gfs2_quota_lock(dip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
         if (error)
                 goto fail;
@@ -596,7 +603,8 @@ fail_end_trans:
         gfs2_trans_end(sdp);
 
 fail_ipreserv:
-        gfs2_inplace_release(dip);
+        if (alloc_required)
+                gfs2_inplace_release(dip);
 
 fail_quota_locks:
         gfs2_quota_unlock(dip);
@@ -647,7 +655,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
         const struct qstr *name = &dentry->d_name;
         struct gfs2_holder ghs[2];
         struct inode *inode = NULL;
-        struct gfs2_inode *dip = GFS2_I(dir);
+        struct gfs2_inode *dip = GFS2_I(dir), *ip;
         struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
         struct gfs2_inum_host inum = { .no_addr = 0, .no_formal_ino = 0 };
         int error;
@@ -657,6 +665,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
         if (!name->len || name->len > GFS2_FNAMESIZE)
                 return -ENAMETOOLONG;
 
+        /* We need a reservation to allocate the new dinode block. The
+           directory ip temporarily points to the reservation, but this is
+           being done to get a set of contiguous blocks for the new dinode.
+           Since this is a create, we don't have a sizehint yet, so it will
+           have to use the minimum reservation size. */
         error = gfs2_rs_alloc(dip);
         if (error)
                 return error;
@@ -694,24 +707,29 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
         if (IS_ERR(inode))
                 goto fail_gunlock2;
 
-        error = gfs2_inode_refresh(GFS2_I(inode));
+        ip = GFS2_I(inode);
+        error = gfs2_inode_refresh(ip);
         if (error)
                 goto fail_gunlock2;
 
-        /* the new inode needs a reservation so it can allocate xattrs. */
-        error = gfs2_rs_alloc(GFS2_I(inode));
-        if (error)
-                goto fail_gunlock2;
+        /* The newly created inode needs a reservation so it can allocate
+           xattrs. At the same time, we want new blocks allocated to the new
+           dinode to be as contiguous as possible. Since we allocated the
+           dinode block under the directory's reservation, we transfer
+           ownership of that reservation to the new inode. The directory
+           doesn't need a reservation unless it needs a new allocation. */
+        ip->i_res = dip->i_res;
+        dip->i_res = NULL;
 
         error = gfs2_acl_create(dip, inode);
         if (error)
                 goto fail_gunlock2;
 
-        error = gfs2_security_init(dip, GFS2_I(inode), name);
+        error = gfs2_security_init(dip, ip, name);
         if (error)
                 goto fail_gunlock2;
 
-        error = link_dinode(dip, name, GFS2_I(inode));
+        error = link_dinode(dip, name, ip);
         if (error)
                 goto fail_gunlock2;
 
@@ -738,6 +756,7 @@ fail_gunlock:
                 iput(inode);
         }
 fail:
+        gfs2_rs_delete(dip);
         if (bh)
                 brelse(bh);
         return error;