cifs: keep a reusable kvec array for receives

Having to continually allocate a new kvec array is expensive. Allocate
one that's big enough, and only reallocate it as needed.

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

2 files changed, 22 insertions, 2 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 55ebf39fb3fd..51ed2de23070 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -292,6 +292,8 @@ struct TCP_Server_Info {
         bool    sec_kerberos;           /* supports plain Kerberos */
         bool    sec_mskerberos;         /* supports legacy MS Kerberos */
         struct delayed_work     echo; /* echo ping workqueue job */
+        struct kvec *iov;       /* reusable kvec array for receives */
+        unsigned int nr_iov;    /* number of kvecs in array */
 #ifdef CONFIG_CIFS_FSCACHE
         struct fscache_cookie   *fscache; /* client index cache cookie */
 #endif
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 4860940b748b..ee70075c5fb1 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -410,6 +410,24 @@ kvec_array_init(struct kvec *new, struct kvec *iov, unsigned int nr_segs,
         return nr_segs;
 }
 
+static struct kvec *
+get_server_iovec(struct TCP_Server_Info *server, unsigned int nr_segs)
+{
+        struct kvec *new_iov;
+
+        if (server->iov && nr_segs <= server->nr_iov)
+                return server->iov;
+
+        /* not big enough -- allocate a new one and release the old */
+        new_iov = kmalloc(sizeof(*new_iov) * nr_segs, GFP_NOFS);
+        if (new_iov) {
+                kfree(server->iov);
+                server->iov = new_iov;
+                server->nr_iov = nr_segs;
+        }
+        return new_iov;
+}
+
 static int
 readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
                   unsigned int nr_segs, unsigned int to_read)
@@ -420,7 +438,7 @@ readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
         struct msghdr smb_msg;
         struct kvec *iov;
 
-        iov = kmalloc(sizeof(*iov_orig) * nr_segs, GFP_NOFS);
+        iov = get_server_iovec(server, nr_segs);
         if (!iov)
                 return -ENOMEM;
 
@@ -464,7 +482,6 @@ readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
                         break;
                 }
         }
-        kfree(iov);
         return total_read;
 }
 
@@ -669,6 +686,7 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
         }
 
         kfree(server->hostname);
+        kfree(server->iov);
         kfree(server);
 
         length = atomic_dec_return(&tcpSesAllocCount);