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, 107 insertions, 0 deletions

diff --git a/fs/afs/vnode.c b/fs/afs/vnode.c
index 0e37f9949cb7..ec814660209f 100644
--- a/fs/afs/vnode.c
+++ b/fs/afs/vnode.c
@@ -753,3 +753,110 @@ no_server:
         _leave(" = %ld [cnt %d]", PTR_ERR(server), orig_dvnode->update_cnt);
         return PTR_ERR(server);
 }
+
+/*
+ * write to a file
+ */
+int afs_vnode_store_data(struct afs_writeback *wb, pgoff_t first, pgoff_t last,
+                         unsigned offset, unsigned to)
+{
+        struct afs_server *server;
+        struct afs_vnode *vnode = wb->vnode;
+        int ret;
+
+        _enter("%s{%x:%u.%u},%x,%lx,%lx,%x,%x",
+               vnode->volume->vlocation->vldb.name,
+               vnode->fid.vid,
+               vnode->fid.vnode,
+               vnode->fid.unique,
+               key_serial(wb->key),
+               first, last, offset, to);
+
+        /* this op will fetch the status */
+        spin_lock(&vnode->lock);
+        vnode->update_cnt++;
+        spin_unlock(&vnode->lock);
+
+        do {
+                /* pick a server to query */
+                server = afs_volume_pick_fileserver(vnode);
+                if (IS_ERR(server))
+                        goto no_server;
+
+                _debug("USING SERVER: %08x\n", ntohl(server->addr.s_addr));
+
+                ret = afs_fs_store_data(server, wb, first, last, offset, to,
+                                        &afs_sync_call);
+
+        } while (!afs_volume_release_fileserver(vnode, server, ret));
+
+        /* adjust the flags */
+        if (ret == 0) {
+                afs_vnode_finalise_status_update(vnode, server);
+                afs_put_server(server);
+        } else {
+                afs_vnode_status_update_failed(vnode, ret);
+        }
+
+        _leave(" = %d", ret);
+        return ret;
+
+no_server:
+        spin_lock(&vnode->lock);
+        vnode->update_cnt--;
+        ASSERTCMP(vnode->update_cnt, >=, 0);
+        spin_unlock(&vnode->lock);
+        return PTR_ERR(server);
+}
+
+/*
+ * set the attributes on a file
+ */
+int afs_vnode_setattr(struct afs_vnode *vnode, struct key *key,
+                      struct iattr *attr)
+{
+        struct afs_server *server;
+        int ret;
+
+        _enter("%s{%x:%u.%u},%x",
+               vnode->volume->vlocation->vldb.name,
+               vnode->fid.vid,
+               vnode->fid.vnode,
+               vnode->fid.unique,
+               key_serial(key));
+
+        /* this op will fetch the status */
+        spin_lock(&vnode->lock);
+        vnode->update_cnt++;
+        spin_unlock(&vnode->lock);
+
+        do {
+                /* pick a server to query */
+                server = afs_volume_pick_fileserver(vnode);
+                if (IS_ERR(server))
+                        goto no_server;
+
+                _debug("USING SERVER: %08x\n", ntohl(server->addr.s_addr));
+
+                ret = afs_fs_setattr(server, key, vnode, attr, &afs_sync_call);
+
+        } while (!afs_volume_release_fileserver(vnode, server, ret));
+
+        /* adjust the flags */
+        if (ret == 0) {
+                afs_vnode_finalise_status_update(vnode, server);
+                afs_put_server(server);
+        } else {
+                afs_vnode_status_update_failed(vnode, ret);
+        }
+
+        _leave(" = %d", ret);
+        return ret;
+
+no_server:
+        spin_lock(&vnode->lock);
+        vnode->update_cnt--;
+        ASSERTCMP(vnode->update_cnt, >=, 0);
+        spin_unlock(&vnode->lock);
+        return PTR_ERR(server);
+}