AFS: implement basic file write support

Implement support for writing to regular AFS files, including:

 (1) write

 (2) truncate

 (3) fsync, fdatasync

 (4) chmod, chown, chgrp, utime.

AFS writeback attempts to batch writes into as chunks as large as it can manage
up to the point that it writes back 65535 pages in one chunk or it meets a
locked page.

Furthermore, if a page has been written to using a particular key, then should
another write to that page use some other key, the first write will be flushed
before the second is allowed to take place.  If the first write fails due to a
security error, then the page will be scrapped and reread before the second
write takes place.

If a page is dirty and the callback on it is broken by the server, then the
dirty data is not discarded (same behaviour as NFS).

Shared-writable mappings are not supported by this patch.

[akpm@linux-foundation.org: fix a bunch of warnings]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 76 insertions, 4 deletions

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index 222c1a3abbb8..04189c47d6a0 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -237,6 +237,70 @@ void afs_flat_call_destructor(struct afs_call *call)
 }
 
 /*
+ * attach the data from a bunch of pages on an inode to a call
+ */
+int afs_send_pages(struct afs_call *call, struct msghdr *msg, struct kvec *iov)
+{
+	struct page *pages[8];
+	unsigned count, n, loop, offset, to;
+	pgoff_t first = call->first, last = call->last;
+	int ret;
+
+	_enter("");
+
+	offset = call->first_offset;
+	call->first_offset = 0;
+
+	do {
+		_debug("attach %lx-%lx", first, last);
+
+		count = last - first + 1;
+		if (count > ARRAY_SIZE(pages))
+			count = ARRAY_SIZE(pages);
+		n = find_get_pages_contig(call->mapping, first, count, pages);
+		ASSERTCMP(n, ==, count);
+
+		loop = 0;
+		do {
+			msg->msg_flags = 0;
+			to = PAGE_SIZE;
+			if (first + loop >= last)
+				to = call->last_to;
+			else
+				msg->msg_flags = MSG_MORE;
+			iov->iov_base = kmap(pages[loop]) + offset;
+			iov->iov_len = to - offset;
+			offset = 0;
+
+			_debug("- range %u-%u%s",
+			       offset, to, msg->msg_flags ? " [more]" : "");
+			msg->msg_iov = (struct iovec *) iov;
+			msg->msg_iovlen = 1;
+
+			/* have to change the state *before* sending the last
+			 * packet as RxRPC might give us the reply before it
+			 * returns from sending the request */
+			if (first + loop >= last)
+				call->state = AFS_CALL_AWAIT_REPLY;
+			ret = rxrpc_kernel_send_data(call->rxcall, msg,
+						     to - offset);
+			kunmap(pages[loop]);
+			if (ret < 0)
+				break;
+		} while (++loop < count);
+		first += count;
+
+		for (loop = 0; loop < count; loop++)
+			put_page(pages[loop]);
+		if (ret < 0)
+			break;
+	} while (first < last);
+
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
  * initiate a call
  */
 int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp,
@@ -253,8 +317,9 @@ int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp,
 	ASSERT(call->type != NULL);
 	ASSERT(call->type->name != NULL);
 
-	_debug("MAKE %p{%s} [%d]",
-	       call, call->type->name, atomic_read(&afs_outstanding_calls));
+	_debug("____MAKE %p{%s,%x} [%d]____",
+	       call, call->type->name, key_serial(call->key),
+	       atomic_read(&afs_outstanding_calls));
 
 	call->wait_mode = wait_mode;
 	INIT_WORK(&call->async_work, afs_process_async_call);
@@ -289,16 +354,23 @@ int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp,
 	msg.msg_iovlen		= 1;
 	msg.msg_control		= NULL;
 	msg.msg_controllen	= 0;
-	msg.msg_flags		= 0;
+	msg.msg_flags		= (call->send_pages ? MSG_MORE : 0);
 
 	/* have to change the state *before* sending the last packet as RxRPC
 	 * might give us the reply before it returns from sending the
 	 * request */
-	call->state = AFS_CALL_AWAIT_REPLY;
+	if (!call->send_pages)
+		call->state = AFS_CALL_AWAIT_REPLY;
 	ret = rxrpc_kernel_send_data(rxcall, &msg, call->request_size);
 	if (ret < 0)
 		goto error_do_abort;
 
+	if (call->send_pages) {
+		ret = afs_send_pages(call, &msg, iov);
+		if (ret < 0)
+			goto error_do_abort;
+	}
+
 	/* at this point, an async call may no longer exist as it may have
 	 * already completed */
 	return wait_mode->wait(call);