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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@redhat.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@uni-dortmund.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.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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