CIFS: Use multicredits for SMB 2.1/3 reads

If we negotiate SMB 2.1 and higher version of the protocol and
a server supports large read buffer size, we need to consume 1
credit per 65536 bytes. So, we need to know how many credits
we have and obtain the required number of them before constructing
a readdata structure in readpages and user read.
Reviewed-by: NShirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: NPavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: NSteve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -1068,6 +1068,7 @@ struct cifs_readdata {
 	struct kvec			iov;
 	unsigned int			pagesz;
 	unsigned int			tailsz;
+	unsigned int			credits;
 	unsigned int			nr_pages;
 	struct page			*pages[];
 };

fs/cifs/file.c

@@ -2917,7 +2917,7 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		     struct cifs_sb_info *cifs_sb, struct list_head *rdata_list)
 {
 	struct cifs_readdata *rdata;
-	unsigned int npages;
+	unsigned int npages, rsize, credits;
 	size_t cur_len;
 	int rc;
 	pid_t pid;
@@ -2931,13 +2931,19 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		pid = current->tgid;
 
 	do {
-		cur_len = min_t(const size_t, len, cifs_sb->rsize);
+		rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
+						   &rsize, &credits);
+		if (rc)
+			break;
+
+		cur_len = min_t(const size_t, len, rsize);
 		npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);
 
 		/* allocate a readdata struct */
 		rdata = cifs_readdata_alloc(npages,
 					    cifs_uncached_readv_complete);
 		if (!rdata) {
+			add_credits_and_wake_if(server, credits, 0);
 			rc = -ENOMEM;
 			break;
 		}
@@ -2953,12 +2959,14 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		rdata->pid = pid;
 		rdata->pagesz = PAGE_SIZE;
 		rdata->read_into_pages = cifs_uncached_read_into_pages;
+		rdata->credits = credits;
 
 		if (!rdata->cfile->invalidHandle ||
 		    !cifs_reopen_file(rdata->cfile, true))
 			rc = server->ops->async_readv(rdata);
 error:
 		if (rc) {
+			add_credits_and_wake_if(server, rdata->credits, 0);
 			kref_put(&rdata->refcount,
 				 cifs_uncached_readdata_release);
 			if (rc == -EAGAIN)
@@ -3458,10 +3466,16 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 	 * the rdata->pages, then we want them in increasing order.
 	 */
 	while (!list_empty(page_list)) {
-		unsigned int i, nr_pages, bytes;
+		unsigned int i, nr_pages, bytes, rsize;
 		loff_t offset;
 		struct page *page, *tpage;
 		struct cifs_readdata *rdata;
+		unsigned credits;
+
+		rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
+						   &rsize, &credits);
+		if (rc)
+			break;
 
 		/*
 		 * Give up immediately if rsize is too small to read an entire
@@ -3469,13 +3483,17 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		 * reach this point however since we set ra_pages to 0 when the
 		 * rsize is smaller than a cache page.
 		 */
-		if (unlikely(cifs_sb->rsize < PAGE_CACHE_SIZE))
+		if (unlikely(rsize < PAGE_CACHE_SIZE)) {
+			add_credits_and_wake_if(server, credits, 0);
 			return 0;
+		}
 
-		rc = readpages_get_pages(mapping, page_list, cifs_sb->rsize,
-					 &tmplist, &nr_pages, &offset, &bytes);
-		if (rc)
+		rc = readpages_get_pages(mapping, page_list, rsize, &tmplist,
+					 &nr_pages, &offset, &bytes);
+		if (rc) {
+			add_credits_and_wake_if(server, credits, 0);
 			break;
+		}
 
 		rdata = cifs_readdata_alloc(nr_pages, cifs_readv_complete);
 		if (!rdata) {
@@ -3487,6 +3505,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 				page_cache_release(page);
 			}
 			rc = -ENOMEM;
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
@@ -3497,6 +3516,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		rdata->pid = pid;
 		rdata->pagesz = PAGE_CACHE_SIZE;
 		rdata->read_into_pages = cifs_readpages_read_into_pages;
+		rdata->credits = credits;
 
 		list_for_each_entry_safe(page, tpage, &tmplist, lru) {
 			list_del(&page->lru);
@@ -3507,6 +3527,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		    !cifs_reopen_file(rdata->cfile, true))
 			rc = server->ops->async_readv(rdata);
 		if (rc) {
+			add_credits_and_wake_if(server, rdata->credits, 0);
 			for (i = 0; i < rdata->nr_pages; i++) {
 				page = rdata->pages[i];
 				lru_cache_add_file(page);

fs/cifs/smb2ops.c

@@ -245,8 +245,9 @@ smb2_negotiate_rsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 	/* start with specified rsize, or default */
 	rsize = volume_info->rsize ? volume_info->rsize : CIFS_DEFAULT_IOSIZE;
 	rsize = min_t(unsigned int, rsize, server->max_read);
-	/* set it to the maximum buffer size value we can send with 1 credit */
-	rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);
+
+	if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
+		rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);
 
 	return rsize;
 }

fs/cifs/smb2pdu.c

@@ -1747,11 +1747,12 @@ smb2_readv_callback(struct mid_q_entry *mid)
 int
 smb2_async_readv(struct cifs_readdata *rdata)
 {
-	int rc;
+	int rc, flags = 0;
 	struct smb2_hdr *buf;
 	struct cifs_io_parms io_parms;
 	struct smb_rqst rqst = { .rq_iov = &rdata->iov,
 				 .rq_nvec = 1 };
+	struct TCP_Server_Info *server;
 
 	cifs_dbg(FYI, "%s: offset=%llu bytes=%u\n",
 		 __func__, rdata->offset, rdata->bytes);
@@ -1762,18 +1763,41 @@ smb2_async_readv(struct cifs_readdata *rdata)
 	io_parms.persistent_fid = rdata->cfile->fid.persistent_fid;
 	io_parms.volatile_fid = rdata->cfile->fid.volatile_fid;
 	io_parms.pid = rdata->pid;
+
+	server = io_parms.tcon->ses->server;
+
 	rc = smb2_new_read_req(&rdata->iov, &io_parms, 0, 0);
-	if (rc)
+	if (rc) {
+		if (rc == -EAGAIN && rdata->credits) {
+			/* credits was reset by reconnect */
+			rdata->credits = 0;
+			/* reduce in_flight value since we won't send the req */
+			spin_lock(&server->req_lock);
+			server->in_flight--;
+			spin_unlock(&server->req_lock);
+		}
 		return rc;
+	}
 
 	buf = (struct smb2_hdr *)rdata->iov.iov_base;
 	/* 4 for rfc1002 length field */
 	rdata->iov.iov_len = get_rfc1002_length(rdata->iov.iov_base) + 4;
 
+	if (rdata->credits) {
+		buf->CreditCharge = cpu_to_le16(DIV_ROUND_UP(rdata->bytes,
+						SMB2_MAX_BUFFER_SIZE));
+		spin_lock(&server->req_lock);
+		server->credits += rdata->credits -
+						le16_to_cpu(buf->CreditCharge);
+		spin_unlock(&server->req_lock);
+		wake_up(&server->request_q);
+		flags = CIFS_HAS_CREDITS;
+	}
+
 	kref_get(&rdata->refcount);
 	rc = cifs_call_async(io_parms.tcon->ses->server, &rqst,
 			     cifs_readv_receive, smb2_readv_callback,
-			     rdata, 0);
+			     rdata, flags);
 	if (rc) {
 		kref_put(&rdata->refcount, cifs_readdata_release);
 		cifs_stats_fail_inc(io_parms.tcon, SMB2_READ_HE);