[PATCH 53/58] [GFS2] gfs2_alloc_required performance

swhiteho
2008-01-21T10:22:44Z

From: Bob Peterson <rpeterso@redhat.com>

This is a small I/O performance enhancement to gfs2. (Actually, it is a rework of
an earlier version I got wrong). The idea here is to check if the write extends
past the last block in the file. If so, the function can save itself a lot of
time and trouble because it knows an allocate will be required. Benchmarks like
iozone should see better performance.

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

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 73dfad7..4356cc2 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1224,6 +1224,11 @@ int gfs2_write_alloc_required(struct gfs2_inode *ip, u64 offset,
unsigned int shift = sdp->sd_sb.sb_bsize_shift;
lblock = offset >> shift;
lblock_stop = (offset + len + sdp->sd_sb.sb_bsize - 1) >> shift;
+ if (lblock_stop > ip->i_di.di_blocks) { /* writing past the
+ last block */
+ *alloc_required = 1;
+ return 0;
+ }
}

for (; lblock < lblock_stop; lblock += extlen) {
--
1.5.1.2