linux-kernel - [06/70] cifs: set ra_pages in backing_dev

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Message-Id: <20110419201043.824344501@clark.kroah.org>
Date:	Tue, 19 Apr 2011 13:08:15 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jeff Layton <jlayton@...hat.com>,
	Steve French <sfrench@...ibm.com>
Subject: [06/70] cifs: set ra_pages in backing_dev_info

2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Layton <jlayton@...hat.com>

commit 2b6c26a0a62cc0bab0ad487533d5581d7c293fef upstream.

Commit 522440ed made cifs set backing_dev_info on the mapping attached
to new inodes. This change caused a fairly significant read performance
regression, as cifs started doing page-sized reads exclusively.

By virtue of the fact that they're allocated as part of cifs_sb_info by
kzalloc, the ra_pages on cifs BDIs get set to 0, which prevents any
readahead. This forces the normal read codepaths to use readpage instead
of readpages causing a four-fold increase in the number of read calls
with the default rsize.

Fix it by setting ra_pages in the BDI to the same value as that in the
default_backing_dev_info.

Fixes https://bugzilla.kernel.org/show_bug.cgi?id=31662

Reported-and-Tested-by: Till <till2.schaefer@...-dortmund.de>
Signed-off-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Steve French <sfrench@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/cifs/cifsfs.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -127,6 +127,7 @@ cifs_read_super(struct super_block *sb,
 		kfree(cifs_sb);
 		return rc;
 	}
+	cifs_sb->bdi.ra_pages = default_backing_dev_info.ra_pages;

 #ifdef CONFIG_CIFS_DFS_UPCALL
 	/* copy mount params to sb for use in submounts */

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