cifs: set ra_pages in backing_dev_info

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

Cc: stable@kernel.org
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>

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 0e0cc60dbde06536cd2c15cd08af2b9a07564c2e..e3352a1ac4790d1135cefc17b553ca47f87f4d51 100644 (file)
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -130,6 +130,7 @@ cifs_read_super(struct super_block *sb, void *data,
                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 */