[Cluster-devel] [PATCH 05/12] gfs2: Remove minor gfs2_journaled_truncate inefficiencies

[Andreas Gruenbacher]

First, this function truncates the file in chunks.  When the original
file size isn't block aligned, each chunk that is truncated will remain
be misaligned.  This is inefficient.

Second, this function doesn't recognize where holes are, so it loops
through them.  For each chunk of a hole, it creates a new transaction.
At least avoid creating another transactions whe the current one is
still empty.  (An better fix would be to skip large holes, of course.)

Signed-off-by: Andreas Gruenbacher <agruenba at redhat.com>
---
 fs/gfs2/bmap.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 963117f704bf..921bf33faa96 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1003,11 +1003,25 @@ static int gfs2_journaled_truncate(struct inode *inode, u64 oldsize, u64 newsize
 	int error;
 
 	while (oldsize != newsize) {
+		struct gfs2_trans *tr;
+		unsigned int offs;
+
 		chunk = oldsize - newsize;
 		if (chunk > max_chunk)
 			chunk = max_chunk;
+
+		offs = oldsize & ~PAGE_MASK;
+		if (offs && chunk > PAGE_SIZE)
+			chunk = offs + ((chunk - offs) & PAGE_MASK);
+
 		truncate_pagecache(inode, oldsize - chunk);
 		oldsize -= chunk;
+
+		/* XXX Is this check sufficient? */
+		tr = current->journal_info;
+		if (!tr->tr_num_revoke)
+			continue;
+
 		gfs2_trans_end(sdp);
 		error = gfs2_trans_begin(sdp, RES_DINODE, GFS2_JTRUNC_REVOKES);
 		if (error)
-- 
2.14.3