From 3cecf4865cd3ea31272750edf38e73c59ff7540c Mon Sep 17 00:00:00 2001 From: Ronnie Sahlberg Date: Tue, 21 Nov 2017 15:08:07 +1100 Subject: [PATCH] cifs: avoid a kmalloc in smb2_send_recv/SendReceive2 for the common case In both functions, use an array of 8 (arbitrary but should be big enough for all current uses) iov and avoid having to kmalloc the array for the common case. If 8 is too small, then fall back to the original behaviour and use kmalloc/kfree. This should not change any behaviour but should save us a tiny amount of cpu cycles. Signed-off-by: Ronnie Sahlberg Signed-off-by: Steve French Reviewed-by: Pavel Shilovsky --- fs/cifs/transport.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index e678307bb7a0..510f41a435c8 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -38,6 +38,9 @@ #include "cifsproto.h" #include "cifs_debug.h" +/* Max number of iovectors we can use off the stack when sending requests. */ +#define CIFS_MAX_IOV_SIZE 8 + void cifs_wake_up_task(struct mid_q_entry *mid) { @@ -803,12 +806,16 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses, const int flags, struct kvec *resp_iov) { struct smb_rqst rqst; - struct kvec *new_iov; + struct kvec s_iov[CIFS_MAX_IOV_SIZE], *new_iov; int rc; - new_iov = kmalloc(sizeof(struct kvec) * (n_vec + 1), GFP_KERNEL); - if (!new_iov) - return -ENOMEM; + if (n_vec + 1 > CIFS_MAX_IOV_SIZE) { + new_iov = kmalloc(sizeof(struct kvec) * (n_vec + 1), + GFP_KERNEL); + if (!new_iov) + return -ENOMEM; + } else + new_iov = s_iov; /* 1st iov is a RFC1001 length followed by the rest of the packet */ memcpy(new_iov + 1, iov, (sizeof(struct kvec) * n_vec)); @@ -823,7 +830,8 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses, rqst.rq_nvec = n_vec + 1; rc = cifs_send_recv(xid, ses, &rqst, resp_buf_type, flags, resp_iov); - kfree(new_iov); + if (n_vec + 1 > CIFS_MAX_IOV_SIZE) + kfree(new_iov); return rc; } @@ -834,15 +842,19 @@ smb2_send_recv(const unsigned int xid, struct cifs_ses *ses, const int flags, struct kvec *resp_iov) { struct smb_rqst rqst; - struct kvec *new_iov; + struct kvec s_iov[CIFS_MAX_IOV_SIZE], *new_iov; int rc; int i; __u32 count; __be32 rfc1002_marker; - new_iov = kmalloc(sizeof(struct kvec) * (n_vec + 1), GFP_KERNEL); - if (!new_iov) - return -ENOMEM; + if (n_vec + 1 > CIFS_MAX_IOV_SIZE) { + new_iov = kmalloc(sizeof(struct kvec) * (n_vec + 1), + GFP_KERNEL); + if (!new_iov) + return -ENOMEM; + } else + new_iov = s_iov; /* 1st iov is an RFC1002 Session Message length */ memcpy(new_iov + 1, iov, (sizeof(struct kvec) * n_vec)); @@ -861,7 +873,8 @@ smb2_send_recv(const unsigned int xid, struct cifs_ses *ses, rqst.rq_nvec = n_vec + 1; rc = cifs_send_recv(xid, ses, &rqst, resp_buf_type, flags, resp_iov); - kfree(new_iov); + if (n_vec + 1 > CIFS_MAX_IOV_SIZE) + kfree(new_iov); return rc; } -- GitLab