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  1. 01 12月, 2008 22 次提交
  3. 21 11月, 2008 1 次提交
    • S
      [CIFS] Do not attempt to close invalidated file handles · ddb4cbfc
      由 Steve French 提交于 
      If a connection with open file handles has gone down
and come back up and reconnected without reopening
the file handle yet, do not attempt to send an SMB close
request for this handle in cifs_close.  We were
checking for the connection being invalid in cifs_close
but since the connection may have been reconnected
we also need to check whether the file handle
was marked invalid (otherwise we could close the
wrong file handle by accident).
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>
      ddb4cbfc
  5. 20 11月, 2008 3 次提交
  7. 19 11月, 2008 1 次提交
  9. 18 11月, 2008 6 次提交
  11. 17 11月, 2008 4 次提交
  13. 16 11月, 2008 1 次提交
    • A
      Fix inotify watch removal/umount races · 8f7b0ba1
      由 Al Viro 提交于 
      Inotify watch removals suck violently.

To kick the watch out we need (in this order) inode->inotify_mutex and
ih->mutex.  That's fine if we have a hold on inode; however, for all
other cases we need to make damn sure we don't race with umount.  We can
*NOT* just grab a reference to a watch - inotify_unmount_inodes() will
happily sail past it and we'll end with reference to inode potentially
outliving its superblock.

Ideally we just want to grab an active reference to superblock if we
can; that will make sure we won't go into inotify_umount_inodes() until
we are done.  Cleanup is just deactivate_super().

However, that leaves a messy case - what if we *are* racing with
umount() and active references to superblock can't be acquired anymore?
We can bump ->s_count, grab ->s_umount, which will almost certainly wait
until the superblock is shut down and the watch in question is pining
for fjords.  That's fine, but there is a problem - we might have hit the
window between ->s_active getting to 0 / ->s_count - below S_BIAS (i.e.
the moment when superblock is past the point of no return and is heading
for shutdown) and the moment when deactivate_super() acquires
->s_umount.

We could just do drop_super() yield() and retry, but that's rather
antisocial and this stuff is luser-triggerable.  OTOH, having grabbed
->s_umount and having found that we'd got there first (i.e.  that
->s_root is non-NULL) we know that we won't race with
inotify_umount_inodes().

So we could grab a reference to watch and do the rest as above, just
with drop_super() instead of deactivate_super(), right? Wrong.  We had
to drop ih->mutex before we could grab ->s_umount.  So the watch
could've been gone already.

That still can be dealt with - we need to save watch->wd, do idr_find()
and compare its result with our pointer.  If they match, we either have
the damn thing still alive or we'd lost not one but two races at once,
the watch had been killed and a new one got created with the same ->wd
at the same address.  That couldn't have happened in inotify_destroy(),
but inotify_rm_wd() could run into that.  Still, "new one got created"
is not a problem - we have every right to kill it or leave it alone,
whatever's more convenient.

So we can use idr_find(...) == watch && watch->inode->i_sb == sb as
"grab it and kill it" check.  If it's been our original watch, we are
fine, if it's a newcomer - nevermind, just pretend that we'd won the
race and kill the fscker anyway; we are safe since we know that its
superblock won't be going away.

And yes, this is far beyond mere "not very pretty"; so's the entire
concept of inotify to start with.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Acked-by: NGreg KH <greg@kroah.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8f7b0ba1
  15. 15 11月, 2008 2 次提交