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, 30 insertions, 1 deletions

diff --git a/fs/gfs2/rgrp.h b/fs/gfs2/rgrp.h
index 5d8314d..ca6e267 100644
--- a/fs/gfs2/rgrp.h
+++ b/fs/gfs2/rgrp.h
@@ -13,6 +13,14 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
+/* Since each block in the file system is represented by two bits in the
+ * bitmap, one 64-bit word in the bitmap will represent 32 blocks.
+ * By reserving 32 blocks at a time, we can optimize / shortcut how we search
+ * through the bitmaps by looking a word at a time.
+ */
+#define RGRP_RSRV_MINBYTES 8
+#define RGRP_RSRV_MINBLKS ((u32)(RGRP_RSRV_MINBYTES * GFS2_NBBY))
+
 struct gfs2_rgrpd;
 struct gfs2_sbd;
 struct gfs2_holder;
@@ -29,6 +37,8 @@ extern void gfs2_free_clones(struct gfs2_rgrpd *rgd);
 extern int gfs2_rgrp_go_lock(struct gfs2_holder *gh);
 extern void gfs2_rgrp_go_unlock(struct gfs2_holder *gh);
 
+extern struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip);
+
 extern int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested);
 extern void gfs2_inplace_release(struct gfs2_inode *ip);
 
@@ -36,6 +46,7 @@ extern int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *n,
 			     bool dinode, u64 *generation);
 
 extern int gfs2_rs_alloc(struct gfs2_inode *ip);
+extern void gfs2_rs_deltree(struct gfs2_blkreserv *rs);
 extern void gfs2_rs_delete(struct gfs2_inode *ip);
 extern void __gfs2_free_blocks(struct gfs2_inode *ip, u64 bstart, u32 blen, int meta);
 extern void gfs2_free_meta(struct gfs2_inode *ip, u64 bstart, u32 blen);
@@ -62,7 +73,7 @@ extern int gfs2_rgrp_send_discards(struct gfs2_sbd *sdp, u64 offset,
 				   const struct gfs2_bitmap *bi, unsigned minlen, u64 *ptrimmed);
 extern int gfs2_fitrim(struct file *filp, void __user *argp);
 
-/* This is how to tell if a reservation is "inplace" reserved: */
+/* This is how to tell if a multi-block reservation is "inplace" reserved: */
 static inline int gfs2_mb_reserved(struct gfs2_inode *ip)
 {
 	if (ip->i_res && ip->i_res->rs_requested)
@@ -70,4 +81,22 @@ static inline int gfs2_mb_reserved(struct gfs2_inode *ip)
 	return 0;
 }
 
+/* This is how to tell if a multi-block reservation is in the rgrp tree: */
+static inline int gfs2_rs_active(struct gfs2_blkreserv *rs)
+{
+	if (rs && rs->rs_bi)
+		return 1;
+	return 0;
+}
+
+static inline u32 gfs2_bi2rgd_blk(const struct gfs2_bitmap *bi, u32 blk)
+{
+	return (bi->bi_start * GFS2_NBBY) + blk;
+}
+
+static inline u64 gfs2_rs_startblk(const struct gfs2_blkreserv *rs)
+{
+	return gfs2_bi2rgd_blk(rs->rs_bi, rs->rs_biblk) + rs->rs_rgd->rd_data0;
+}
+
 #endif /* __RGRP_DOT_H__ */