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, 46 insertions, 1 deletions

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 9c984cc42cc9..515a5d12d8fb 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -209,7 +209,7 @@ bad_inode:
  */
 void afs_zap_data(struct afs_vnode *vnode)
 {
-	kenter("zap data {%x:%u}", vnode->fid.vid, vnode->fid.vnode);
+	_enter("zap data {%x:%u}", vnode->fid.vid, vnode->fid.vnode);
 
 	/* nuke all the non-dirty pages that aren't locked, mapped or being
 	 * written back */
@@ -334,6 +334,7 @@ void afs_clear_inode(struct inode *inode)
 		vnode->server = NULL;
 	}
 
+	ASSERT(list_empty(&vnode->writebacks));
 	ASSERT(!vnode->cb_promised);
 
 #ifdef AFS_CACHING_SUPPORT
@@ -350,3 +351,47 @@ void afs_clear_inode(struct inode *inode)
 
 	_leave("");
 }
+
+/*
+ * set the attributes of an inode
+ */
+int afs_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
+	struct key *key;
+	int ret;
+
+	_enter("{%x:%u},{n=%s},%x",
+	       vnode->fid.vid, vnode->fid.vnode, dentry->d_name.name,
+	       attr->ia_valid);
+
+	if (!(attr->ia_valid & (ATTR_SIZE | ATTR_MODE | ATTR_UID | ATTR_GID |
+				ATTR_MTIME))) {
+		_leave(" = 0 [unsupported]");
+		return 0;
+	}
+
+	/* flush any dirty data outstanding on a regular file */
+	if (S_ISREG(vnode->vfs_inode.i_mode)) {
+		filemap_write_and_wait(vnode->vfs_inode.i_mapping);
+		afs_writeback_all(vnode);
+	}
+
+	if (attr->ia_valid & ATTR_FILE) {
+		key = attr->ia_file->private_data;
+	} else {
+		key = afs_request_key(vnode->volume->cell);
+		if (IS_ERR(key)) {
+			ret = PTR_ERR(key);
+			goto error;
+		}
+	}
+
+	ret = afs_vnode_setattr(vnode, key, attr);
+	if (!(attr->ia_valid & ATTR_FILE))
+		key_put(key);
+
+error:
+	_leave(" = %d", ret);
+	return ret;
+}