ceph: set io_pages bdi hint

This patch sets the io_pages bdi hint based on the rsize mount option.
Without this patch large buffered reads (request size > max readahead)
are processed sequentially in chunks of the readahead size (i.e. read
requests are sent out up to the readahead size, then the
do_generic_file_read() function waits until the first page is received).

With this patch read requests are sent out at once up to the size
specified in the rsize mount option (default: 64 MB).

Signed-off-by: Andreas Gerstmayr <andreas.gerstmayr@catalysts.cc>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Yan, Zheng <zyan@redhat.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/Documentation/filesystems/ceph.txt b/Documentation/filesystems/ceph.txt
index f5306ee40ea9..0b302a11718a 100644
--- a/Documentation/filesystems/ceph.txt
+++ b/Documentation/filesystems/ceph.txt
@@ -98,11 +98,10 @@ Mount Options
         size.
 
   rsize=X
-        Specify the maximum read size in bytes.  By default there is no
-        maximum.
+        Specify the maximum read size in bytes.  Default: 64 MB.
 
   rasize=X
-        Specify the maximum readahead.
+        Specify the maximum readahead.  Default: 8 MB.
 
   mount_timeout=X
         Specify the timeout value for mount (in seconds), in the case