On Fri, 16 Mar 2012 18:09:33 +0300
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> While in CIFS/SMB we have 16 bit mid, in SMB2 it is 64 bit.
> Convert the existing field to 64 bit and mask off higher bits
> for CIFS/SMB.
>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
> fs/cifs/cifsglob.h | 2 +-
> fs/cifs/cifsproto.h | 2 +-
> fs/cifs/misc.c | 84 ++++++++++++++++++++++++++++-----------------------
> 3 files changed, 48 insertions(+), 40 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index a403398..b213458 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -282,7 +282,7 @@ struct TCP_Server_Info {
> vcnumbers */
> int capabilities; /* allow selective disabling of caps by smb sess */
> int timeAdj; /* Adjust for difference in server time zone in sec */
> - __u16 CurrentMid; /* multiplex id - rotating counter */
> + __u64 CurrentMid; /* multiplex id - rotating counter */
It occurs to me that a simpler way to do this might be to turn this
into a union with a u16 and u64 field. This works just as well though...
> char cryptkey[CIFS_CRYPTO_KEY_SIZE]; /* used by ntlm, ntlmv2 etc */
> /* 16th byte of RFC1001 workstation name is always null */
> char workstation_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index db38a40..8958721 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -115,7 +115,7 @@ extern int small_smb_init_no_tc(const int smb_cmd, const int wct,
> void **request_buf);
> extern int CIFS_SessSetup(unsigned int xid, struct cifs_ses *ses,
> const struct nls_table *nls_cp);
> -extern __u16 GetNextMid(struct TCP_Server_Info *server);
> +extern __u64 GetNextMid(struct TCP_Server_Info *server);
> extern struct timespec cifs_NTtimeToUnix(__le64 utc_nanoseconds_since_1601);
> extern u64 cifs_UnixTimeToNT(struct timespec);
> extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time,
> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
> index 88459d0..0b743b7 100644
> --- a/fs/cifs/misc.c
> +++ b/fs/cifs/misc.c
> @@ -213,54 +213,61 @@ cifs_small_buf_release(void *buf_to_free)
> }
>
> /*
> - Find a free multiplex id (SMB mid). Otherwise there could be
> - mid collisions which might cause problems, demultiplexing the
> - wrong response to this request. Multiplex ids could collide if
> - one of a series requests takes much longer than the others, or
> - if a very large number of long lived requests (byte range
> - locks or FindNotify requests) are pending. No more than
> - 64K-1 requests can be outstanding at one time. If no
> - mids are available, return zero. A future optimization
> - could make the combination of mids and uid the key we use
> - to demultiplex on (rather than mid alone).
> - In addition to the above check, the cifs demultiplex
> - code already used the command code as a secondary
> - check of the frame and if signing is negotiated the
> - response would be discarded if the mid were the same
> - but the signature was wrong. Since the mid is not put in the
> - pending queue until later (when it is about to be dispatched)
> - we do have to limit the number of outstanding requests
> - to somewhat less than 64K-1 although it is hard to imagine
> - so many threads being in the vfs at one time.
> -*/
> -__u16 GetNextMid(struct TCP_Server_Info *server)
> + * Find a free multiplex id (SMB mid). Otherwise there could be
> + * mid collisions which might cause problems, demultiplexing the
> + * wrong response to this request. Multiplex ids could collide if
> + * one of a series requests takes much longer than the others, or
> + * if a very large number of long lived requests (byte range
> + * locks or FindNotify requests) are pending. No more than
> + * 64K-1 requests can be outstanding at one time. If no
> + * mids are available, return zero. A future optimization
> + * could make the combination of mids and uid the key we use
> + * to demultiplex on (rather than mid alone).
> + * In addition to the above check, the cifs demultiplex
> + * code already used the command code as a secondary
> + * check of the frame and if signing is negotiated the
> + * response would be discarded if the mid were the same
> + * but the signature was wrong. Since the mid is not put in the
> + * pending queue until later (when it is about to be dispatched)
> + * we do have to limit the number of outstanding requests
> + * to somewhat less than 64K-1 although it is hard to imagine
> + * so many threads being in the vfs at one time.
> + */
> +__u64 GetNextMid(struct TCP_Server_Info *server)
> {
> - __u16 mid = 0;
> - __u16 last_mid;
> + __u64 mid = 0;
> + __u16 last_mid, cur_mid;
> bool collision;
>
> spin_lock(&GlobalMid_Lock);
> - last_mid = server->CurrentMid; /* we do not want to loop forever */
> - server->CurrentMid++;
> - /* This nested loop looks more expensive than it is.
> - In practice the list of pending requests is short,
> - fewer than 50, and the mids are likely to be unique
> - on the first pass through the loop unless some request
> - takes longer than the 64 thousand requests before it
> - (and it would also have to have been a request that
> - did not time out) */
> - while (server->CurrentMid != last_mid) {
> +
> + /* mid is 16 bit only for CIFS/SMB */
> + cur_mid = (__u16)((server->CurrentMid) & 0xffff);
> + /* we do not want to loop forever */
> + last_mid = cur_mid;
> + cur_mid++;
> +
> + /*
> + * This nested loop looks more expensive than it is.
> + * In practice the list of pending requests is short,
> + * fewer than 50, and the mids are likely to be unique
> + * on the first pass through the loop unless some request
> + * takes longer than the 64 thousand requests before it
> + * (and it would also have to have been a request that
> + * did not time out).
> + */
> + while (cur_mid != last_mid) {
> struct mid_q_entry *mid_entry;
> unsigned int num_mids;
>
> collision = false;
> - if (server->CurrentMid == 0)
> - server->CurrentMid++;
> + if (cur_mid == 0)
> + cur_mid++;
>
> num_mids = 0;
> list_for_each_entry(mid_entry, &server->pending_mid_q, qhead) {
> ++num_mids;
> - if (mid_entry->mid == server->CurrentMid &&
> + if (mid_entry->mid == cur_mid &&
> mid_entry->midState == MID_REQUEST_SUBMITTED) {
> /* This mid is in use, try a different one */
> collision = true;
> @@ -282,10 +289,11 @@ __u16 GetNextMid(struct TCP_Server_Info *server)
> server->tcpStatus = CifsNeedReconnect;
>
> if (!collision) {
> - mid = server->CurrentMid;
> + mid = (__u64)cur_mid;
> + server->CurrentMid = mid;
> break;
> }
> - server->CurrentMid++;
> + cur_mid++;
> }
> spin_unlock(&GlobalMid_Lock);
> return mid;
Not directly related to this patch, but should we move all of these mid
operations under the req_lock instead of the GlobalMid_Lock? The global
spinlock is a bottleneck and all of the structures involved should be
per-server anyway.
Anyway, I think this looks ok
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
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