ceph: ensure prealloc_blob is in place when removing xattr

In __ceph_build_xattrs_blob(), if a ceph inode's extended attributes
are marked dirty, all attributes recorded in its rb_tree index are
formatted into a "blob" buffer.  The target buffer is recorded in
ceph_inode->i_xattrs.prealloc_blob, and it is expected to exist and
be of sufficient size to hold the attributes.

The extended attributes are marked dirty in two cases: when a new
attribute is added to the inode; or when one is removed.  In the
former case work is done to ensure the prealloc_blob buffer is
properly set up, but in the latter it is not.

Change the logic in ceph_removexattr() so it matches what is
done in ceph_setxattr().  Note that this is done in a way that
keeps the two blocks of code nearly identical, in anticipation
of a subsequent patch that encapsulates some of this logic into
one or more helper routines.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index a5e36e4..857214a 100644 (file)
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -818,6 +818,7 @@ int ceph_removexattr(struct dentry *dentry, const char *name)
        struct ceph_vxattr_cb *vxattrs = ceph_inode_vxattrs(inode);
        int issued;
        int err;
+       int required_blob_size;
        int dirty;
 
        if (ceph_snap(inode) != CEPH_NOSNAP)
@@ -833,14 +834,34 @@ int ceph_removexattr(struct dentry *dentry, const char *name)
                        return -EOPNOTSUPP;
        }
 
+       err = -ENOMEM;
        spin_lock(&ci->i_ceph_lock);
        __build_xattrs(inode);
+retry:
        issued = __ceph_caps_issued(ci, NULL);
        dout("removexattr %p issued %s\n", inode, ceph_cap_string(issued));
 
        if (!(issued & CEPH_CAP_XATTR_EXCL))
                goto do_sync;
 
+       required_blob_size = __get_required_blob_size(ci, 0, 0);
+
+       if (!ci->i_xattrs.prealloc_blob ||
+           required_blob_size > ci->i_xattrs.prealloc_blob->alloc_len) {
+               struct ceph_buffer *blob;
+
+               spin_unlock(&ci->i_ceph_lock);
+               dout(" preaallocating new blob size=%d\n", required_blob_size);
+               blob = ceph_buffer_new(required_blob_size, GFP_NOFS);
+               if (!blob)
+                       goto out;
+               spin_lock(&ci->i_ceph_lock);
+               if (ci->i_xattrs.prealloc_blob)
+                       ceph_buffer_put(ci->i_xattrs.prealloc_blob);
+               ci->i_xattrs.prealloc_blob = blob;
+               goto retry;
+       }
+
        err = __remove_xattr_by_name(ceph_inode(inode), name);
        dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_XATTR_EXCL);
        ci->i_xattrs.dirty = true;
@@ -853,6 +874,7 @@ int ceph_removexattr(struct dentry *dentry, const char *name)
 do_sync:
        spin_unlock(&ci->i_ceph_lock);
        err = ceph_send_removexattr(dentry, name);
+out:
        return err;
 }