Having to continually allocate a new kvec array is expensive. Allocate
one that's big enough, and only reallocate it as needed. Also, we need
to use GFP_NOFS here to ensure that this doesn't deadlock.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/cifs/cifsglob.h | 2 ++
fs/cifs/connect.c | 26 ++++++++++++++++++++------
2 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index a37452d..c3caa78 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -287,6 +287,8 @@ 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 08c6b0e..e16c04b 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)
@@ -420,11 +438,7 @@ readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
struct msghdr smb_msg;
struct kvec *iov;
- /*
- * FIXME: allocation here may cause deadlocks under memory pressure.
- * Switch this to use a fixed, per-socket buffer.
- */
- iov = kmalloc(sizeof(*iov_orig) * nr_segs, GFP_KERNEL);
+ iov = get_server_iovec(server, nr_segs);
if (!iov)
return -ENOMEM;
@@ -468,7 +482,6 @@ readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
break;
}
}
- kfree(iov);
return total_read;
}
@@ -686,6 +699,7 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
}
kfree(server->hostname);
+ kfree(server->iov);
kfree(server);
length = atomic_dec_return(&tcpSesAllocCount);
--
1.7.6
--
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