cifs: tune bdi.ra_pages in accordance with the rsize

Tune bdi.ra_pages to be a multiple of the rsize. This prevents the VFS
from asking for pages that require small reads to satisfy.

Reviewed-and-Tested-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 06dfaacfea5d..f70d87d6ba61 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3182,6 +3182,22 @@ cifs_get_volume_info(char *mount_data, const char *devname)
         return volume_info;
 }
 
+/* make sure ra_pages is a multiple of rsize */
+static inline unsigned int
+cifs_ra_pages(struct cifs_sb_info *cifs_sb)
+{
+        unsigned int reads;
+        unsigned int rsize_pages = cifs_sb->rsize / PAGE_CACHE_SIZE;
+
+        if (rsize_pages >= default_backing_dev_info.ra_pages)
+                return default_backing_dev_info.ra_pages;
+        else if (rsize_pages == 0)
+                return rsize_pages;
+
+        reads = default_backing_dev_info.ra_pages / rsize_pages;
+        return reads * rsize_pages;
+}
+
 int
 cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 {
@@ -3200,8 +3216,6 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
         if (rc)
                 return rc;
 
-        cifs_sb->bdi.ra_pages = default_backing_dev_info.ra_pages;
-
 #ifdef CONFIG_CIFS_DFS_UPCALL
 try_mount_again:
         /* cleanup activities if we're chasing a referral */
@@ -3269,6 +3283,9 @@ try_mount_again:
         cifs_sb->wsize = cifs_negotiate_wsize(tcon, volume_info);
         cifs_sb->rsize = cifs_negotiate_rsize(tcon, volume_info);
 
+        /* tune readahead according to rsize */
+        cifs_sb->bdi.ra_pages = cifs_ra_pages(cifs_sb);
+
 remote_path_check:
 #ifdef CONFIG_CIFS_DFS_UPCALL
         /*