diff options
Diffstat (limited to 'fs/cifs/misc.c')
| -rw-r--r-- | fs/cifs/misc.c | 84 |
1 files changed, 77 insertions, 7 deletions
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c index 20ae4153f79..beeff828416 100644 --- a/fs/cifs/misc.c +++ b/fs/cifs/misc.c @@ -34,8 +34,6 @@ extern mempool_t *cifs_sm_req_poolp; extern mempool_t *cifs_req_poolp; extern struct task_struct * oplockThread; -static __u16 GlobalMid; /* multiplex id - rotating counter */ - /* The xid serves as a useful identifier for each incoming vfs request, in a similar way to the mid which is useful to track each sent smb, and CurrentXid can also provide a running counter (although it @@ -51,6 +49,8 @@ _GetXid(void) GlobalTotalActiveXid++; if (GlobalTotalActiveXid > GlobalMaxActiveXid) GlobalMaxActiveXid = GlobalTotalActiveXid; /* keep high water mark for number of simultaneous vfs ops in our filesystem */ + if(GlobalTotalActiveXid > 65000) + cFYI(1,("warning: more than 65000 requests active")); xid = GlobalCurrentXid++; spin_unlock(&GlobalMid_Lock); return xid; @@ -218,6 +218,76 @@ cifs_small_buf_release(void *buf_to_free) return; } +/* + 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) +{ + __u16 mid = 0; + __u16 last_mid; + int collision; + + if(server == NULL) + return mid; + + 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) { + struct list_head *tmp; + struct mid_q_entry *mid_entry; + + collision = 0; + if(server->CurrentMid == 0) + server->CurrentMid++; + + list_for_each(tmp, &server->pending_mid_q) { + mid_entry = list_entry(tmp, struct mid_q_entry, qhead); + + if ((mid_entry->mid == server->CurrentMid) && + (mid_entry->midState == MID_REQUEST_SUBMITTED)) { + /* This mid is in use, try a different one */ + collision = 1; + break; + } + } + if(collision == 0) { + mid = server->CurrentMid; + break; + } + server->CurrentMid++; + } + spin_unlock(&GlobalMid_Lock); + return mid; +} + +/* NB: MID can not be set if treeCon not passed in, in that + case it is responsbility of caller to set the mid */ void header_assemble(struct smb_hdr *buffer, char smb_command /* command */ , const struct cifsTconInfo *treeCon, int word_count @@ -233,7 +303,8 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ , (2 * word_count) + sizeof (struct smb_hdr) - 4 /* RFC 1001 length field does not count */ + 2 /* for bcc field itself */ ; - /* Note that this is the only network field that has to be converted to big endian and it is done just before we send it */ + /* Note that this is the only network field that has to be converted + to big endian and it is done just before we send it */ buffer->Protocol[0] = 0xFF; buffer->Protocol[1] = 'S'; @@ -245,8 +316,6 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ , buffer->Pid = cpu_to_le16((__u16)current->tgid); buffer->PidHigh = cpu_to_le16((__u16)(current->tgid >> 16)); spin_lock(&GlobalMid_Lock); - GlobalMid++; - buffer->Mid = GlobalMid; spin_unlock(&GlobalMid_Lock); if (treeCon) { buffer->Tid = treeCon->tid; @@ -256,8 +325,9 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ , if (treeCon->ses->capabilities & CAP_STATUS32) { buffer->Flags2 |= SMBFLG2_ERR_STATUS; } - - buffer->Uid = treeCon->ses->Suid; /* always in LE format */ + /* Uid is not converted */ + buffer->Uid = treeCon->ses->Suid; + buffer->Mid = GetNextMid(treeCon->ses->server); if(multiuser_mount != 0) { /* For the multiuser case, there are few obvious technically */ /* possible mechanisms to match the local linux user (uid) */ |