Eventually we'll want to allow cifsd to read data directly into the pagecache. In order to do that we'll need a routine that can take a kvec array and pass that directly to kernel_recvmsg.
Unfortunately though, the kernel's recvmsg routines modify the kvec array that gets passed in, so we need to use a copy of the kvec array and refresh that copy on each pass through the loop. Signed-off-by: Jeff Layton <[email protected]> --- fs/cifs/connect.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++----- 1 files changed, 65 insertions(+), 7 deletions(-) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 358e0b0..430e563 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -375,14 +375,58 @@ server_unresponsive(struct TCP_Server_Info *server) return false; } +/* + * kvec_array_setup - clone a kvec array, and advance into it + * @new: pointer to memory for cloned array + * @iov: pointer to original array + * @nr_segs: number of members in original array + * @bytes: number of bytes to advance into the cloned array + * + * This function will copy the array provided in iov to a section of memory + * and advance the specified number of bytes into the new array. It returns + * the number of segments in the new array. "new" must be at least as big as + * the original iov array. + */ +static unsigned int +kvec_array_init(struct kvec *new, struct kvec *iov, unsigned int nr_segs, + size_t bytes) +{ + size_t base = 0; + + while (bytes || !iov->iov_len) { + int copy = min(bytes, iov->iov_len); + + bytes -= copy; + base += copy; + if (iov->iov_len == base) { + iov++; + nr_segs--; + base = 0; + } + } + memcpy(new, iov, sizeof(*iov) * nr_segs); + new->iov_base += base; + new->iov_len -= base; + return nr_segs; +} + static int -read_from_socket(struct TCP_Server_Info *server, char *buf, - unsigned int to_read) +readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig, + unsigned int nr_segs, unsigned int to_read) { int length = 0; int total_read; + unsigned int segs; struct msghdr smb_msg; - struct kvec iov; + 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); + if (!iov) + return -ENOMEM; smb_msg.msg_control = NULL; smb_msg.msg_controllen = 0; @@ -393,10 +437,11 @@ read_from_socket(struct TCP_Server_Info *server, char *buf, break; } - iov.iov_base = buf + total_read; - iov.iov_len = to_read; - length = kernel_recvmsg(server->ssocket, &smb_msg, &iov, 1, - to_read, 0); + segs = kvec_array_init(iov, iov_orig, nr_segs, total_read); + + length = kernel_recvmsg(server->ssocket, &smb_msg, + iov, segs, to_read, 0); + if (server->tcpStatus == CifsExiting) { total_read = -ESHUTDOWN; break; @@ -423,9 +468,22 @@ read_from_socket(struct TCP_Server_Info *server, char *buf, break; } } + kfree(iov); return total_read; } +static int +read_from_socket(struct TCP_Server_Info *server, char *buf, + unsigned int to_read) +{ + struct kvec iov; + + iov.iov_base = buf; + iov.iov_len = to_read; + + return readv_from_socket(server, &iov, 1, to_read); +} + static bool check_rfc1002_header(struct TCP_Server_Info *server, char *buf) { -- 1.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
