tree 51f8ac8ab4f06207a406cb9e917a48d71616235c
parent e57ac68378a287d6336d187b26971f35f7ee7251
author Miklos Szeredi <mszeredi@suse.cz> 1192702018 -0700
committer Linus Torvalds <torvalds@woody.linux-foundation.org> 1192743450 -0700

fuse: fix race between getattr and write

Getattr and lookup operations can be running in parallel to attribute changing
operations, such as write and setattr.

This means, that if for example getattr was slower than a write, the cached
size attribute could be set to a stale value.

To prevent this race, introduce a per-filesystem attribute version counter.
This counter is incremented whenever cached attributes are modified, and the
incremented value stored in the inode.

Before storing new attributes in the cache, getattr and lookup check, using
the version number, whether the attributes have been modified during the
request's lifetime.  If so, the returned attributes are not cached, because
they might be stale.

Thanks to Jakub Bogusz for the bug report and test program.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Jakub Bogusz <jakub.bogusz@gemius.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>