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From: Andreas Gruenbacher <agruenba@redhat.com>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [PATCH 2/2] gfs2: Extended attribute readahead optimization
Date: Sun,  1 Nov 2015 20:02:59 +0100	[thread overview]
Message-ID: <1446404579-5211-3-git-send-email-agruenba@redhat.com> (raw)
In-Reply-To: <1446404579-5211-1-git-send-email-agruenba@redhat.com>

Instead of submitting separate bio for the inode and its extended
attributes, submit a single bio for both when possible.  The entire
request becomes a normal read, not a readahead.

To keep track of the buffer heads that make up the bio, we allocate
temporary buffer head arrays: in the endio handler, it would also be
possible to compute the buffer head block numbers from the bio and to
grab the buffer heads with gfs2_getbuf, but the code would become even
messier.
---
 fs/gfs2/meta_io.c | 94 ++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 76 insertions(+), 18 deletions(-)

diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index 0f24828..e650127 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -187,19 +187,63 @@ struct buffer_head *gfs2_meta_new(struct gfs2_glock *gl, u64 blkno)
 	return bh;
 }
 
-static void gfs2_meta_readahead(struct gfs2_glock *gl, u64 blkno)
+struct gfs2_meta_read {
+	int num;
+	struct buffer_head *bhs[0];
+};
+
+static void gfs2_meta_read_endio(struct bio *bio) {
+	struct gfs2_meta_read *r = bio->bi_private;
+	int i;
+
+	for (i = 0; i < r->num; i++) {
+		struct buffer_head *bh = r->bhs[i];
+
+		if (unlikely(bio_flagged(bio, BIO_QUIET)))
+			set_bit(BH_Quiet, &bh->b_state);
+
+		bh->b_end_io(bh, !bio->bi_error);
+	}
+	bio_put(bio);
+	kfree(r);
+}
+
+/*
+ * (See submit_bh_wbc.)
+ */
+static void gfs2_submit_bhs(int rw, struct buffer_head *bhs[], int num)
 {
-	struct buffer_head *bh;
+	struct gfs2_meta_read *r;
+	struct buffer_head *bh = bhs[0];
+	struct bio *bio;
+	int i;
 
-	bh = gfs2_getbuf(gl, blkno, 1);
-	lock_buffer(bh);
-	if (buffer_uptodate(bh)) {
-		unlock_buffer(bh);
-		brelse(bh);
+	if (!num)
+		return;
+
+	if (num == 1) {
+		bh->b_end_io = end_buffer_read_sync;
+		submit_bh(rw, bh);
 		return;
 	}
-	bh->b_end_io = end_buffer_read_sync;
-	submit_bh(READA | REQ_META | REQ_PRIO, bh);
+
+	r = kmalloc(sizeof(*r) + num * sizeof(r->bhs[0]),
+		    GFP_NOIO | __GFP_NOFAIL);
+	r->num = num;
+	for (i = 0; i < num; i++)
+		r->bhs[i] = bhs[i];
+
+	bio = bio_alloc(GFP_NOIO, num);
+	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
+	bio->bi_bdev = bh->b_bdev;
+	for (i = 0; i < num; i++) {
+		bh = bhs[i];
+		bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
+	}
+	bio->bi_end_io = gfs2_meta_read_endio;
+	bio->bi_private = r;
+
+	submit_bio(rw, bio);
 }
 
 /**
@@ -216,7 +260,8 @@ int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags,
 		   int rahead, struct buffer_head **bhp)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
-	struct buffer_head *bh;
+	struct buffer_head *bh, *bhs[2];
+	int num = 0;
 
 	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
 		*bhp = NULL;
@@ -228,18 +273,31 @@ int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags,
 	lock_buffer(bh);
 	if (buffer_uptodate(bh)) {
 		unlock_buffer(bh);
-		if (rahead)
-			gfs2_meta_readahead(gl, blkno + 1);
-		return 0;
+		flags &= ~DIO_WAIT;
+	} else {
+		bh->b_end_io = end_buffer_read_sync;
+		get_bh(bh);
+		bhs[num++] = bh;
 	}
-	bh->b_end_io = end_buffer_read_sync;
-	get_bh(bh);
-	submit_bh(READ_SYNC | REQ_META | REQ_PRIO, bh);
-	if (rahead)
-		gfs2_meta_readahead(gl, blkno + 1);
+
+	if (rahead) {
+		bh = gfs2_getbuf(gl, blkno + 1, CREATE);
+
+		lock_buffer(bh);
+		if (buffer_uptodate(bh)) {
+			unlock_buffer(bh);
+			brelse(bh);
+		} else {
+			bh->b_end_io = end_buffer_read_sync;
+			bhs[num++] = bh;
+		}
+	}
+
+	gfs2_submit_bhs(READ_SYNC | REQ_META | REQ_PRIO, bhs, num);
 	if (!(flags & DIO_WAIT))
 		return 0;
 
+	bh = *bhp;
 	wait_on_buffer(bh);
 	if (unlikely(!buffer_uptodate(bh))) {
 		struct gfs2_trans *tr = current->journal_info;
-- 
2.5.0



  parent reply	other threads:[~2015-11-01 19:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-01 19:02 [Cluster-devel] [PATCH 0/2] Extended attribute readahead Andreas Gruenbacher
2015-11-01 19:02 ` [Cluster-devel] [PATCH 1/2] gfs2: " Andreas Gruenbacher
2015-11-03 17:29   ` Bob Peterson
2015-11-03 19:02     ` Steven Whitehouse
2015-11-03 20:18       ` Andreas Gruenbacher
2015-11-01 19:02 ` Andreas Gruenbacher [this message]
2015-11-12 13:44   ` [Cluster-devel] [PATCH 2/2] gfs2: Extended attribute readahead optimization Steven Whitehouse
2015-11-12 15:33     ` Andreas Gruenbacher
2015-11-12 20:15       ` Andreas Gruenbacher
2015-11-12 20:33         ` Steven Whitehouse
2015-11-13 22:24           ` Andreas Gruenbacher
2015-11-16 18:14             ` Bob Peterson
2015-11-13 13:48         ` Bob Peterson

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