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authorJohn Muir <john@jmuir.com>2011-12-06 21:50:06 +0100
committerMiklos Szeredi <mszeredi@suse.cz>2011-12-13 11:58:49 +0100
commit451d0f599934fd97faf54a5d7954b518e66192cb (patch)
tree6dd7a6fcdc8ff3bc50dec37b114c447b3b1d7ba1 /fs/fuse/dev.c
parentb18da0c56e9ff43a007b6c8e302c62e720964151 (diff)
FUSE: Notifying the kernel of deletion.
Allows a FUSE file-system to tell the kernel when a file or directory is deleted. If the specified dentry has the specified inode number, the kernel will unhash it. The current 'fuse_notify_inval_entry' does not cause the kernel to clean up directories that are in use properly, and as a result the users of those directories see incorrect semantics from the file-system. The error condition seen when 'fuse_notify_inval_entry' is used to notify of a deleted directory is avoided when 'fuse_notify_delete' is used instead. The following scenario demonstrates the difference: 1. User A chdirs into 'testdir' and starts reading 'testfile'. 2. User B rm -rf 'testdir'. 3. User B creates 'testdir'. 4. User C chdirs into 'testdir'. If you run the above within the same machine on any file-system (including fuse file-systems), there is no problem: user C is able to chdir into the new testdir. The old testdir is removed from the dentry tree, but still open by user A. If operations 2 and 3 are performed via the network such that the fuse file-system uses one of the notify functions to tell the kernel that the nodes are gone, then the following error occurs for user C while user A holds the original directory open: muirj@empacher:~> ls /test/testdir ls: cannot access /test/testdir: No such file or directory The issue here is that the kernel still has a dentry for testdir, and so it is requesting the attributes for the old directory, while the file-system is responding that the directory no longer exists. If on the other hand, if the file-system can notify the kernel that the directory is deleted using the new 'fuse_notify_delete' function, then the above ls will find the new directory as expected. Signed-off-by: John Muir <john@jmuir.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs/fuse/dev.c')
-rw-r--r--fs/fuse/dev.c57
1 files changed, 56 insertions, 1 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 2aaf3eaaf13..5f3368ab0fa 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1378,7 +1378,59 @@ static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
down_read(&fc->killsb);
err = -ENOENT;
if (fc->sb)
- err = fuse_reverse_inval_entry(fc->sb, outarg.parent, &name);
+ err = fuse_reverse_inval_entry(fc->sb, outarg.parent, 0, &name);
+ up_read(&fc->killsb);
+ kfree(buf);
+ return err;
+
+err:
+ kfree(buf);
+ fuse_copy_finish(cs);
+ return err;
+}
+
+static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
+ struct fuse_copy_state *cs)
+{
+ struct fuse_notify_delete_out outarg;
+ int err = -ENOMEM;
+ char *buf;
+ struct qstr name;
+
+ buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+ if (!buf)
+ goto err;
+
+ err = -EINVAL;
+ if (size < sizeof(outarg))
+ goto err;
+
+ err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+ if (err)
+ goto err;
+
+ err = -ENAMETOOLONG;
+ if (outarg.namelen > FUSE_NAME_MAX)
+ goto err;
+
+ err = -EINVAL;
+ if (size != sizeof(outarg) + outarg.namelen + 1)
+ goto err;
+
+ name.name = buf;
+ name.len = outarg.namelen;
+ err = fuse_copy_one(cs, buf, outarg.namelen + 1);
+ if (err)
+ goto err;
+ fuse_copy_finish(cs);
+ buf[outarg.namelen] = 0;
+ name.hash = full_name_hash(name.name, name.len);
+
+ down_read(&fc->killsb);
+ err = -ENOENT;
+ if (fc->sb)
+ err = fuse_reverse_inval_entry(fc->sb, outarg.parent,
+ outarg.child, &name);
up_read(&fc->killsb);
kfree(buf);
return err;
@@ -1597,6 +1649,9 @@ static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
case FUSE_NOTIFY_RETRIEVE:
return fuse_notify_retrieve(fc, size, cs);
+ case FUSE_NOTIFY_DELETE:
+ return fuse_notify_delete(fc, size, cs);
+
default:
fuse_copy_finish(cs);
return -EINVAL;