Hi, the following patch fixes the symlink bug I mentioned a few days ago.
Thanks for your comments.
Louis
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
On Mon, Jun 16, 2008 at 08:09:11PM +0200, Louis Rilling wrote:
> This patch introduces a similar (weird?) behavior as with mkdir failures making
> rmdir fail: if symlink() races with rmdir() of the parent directory (or its
> youngest user-created ancestor if parent is a default group) or rmdir() of the
> target directory, and then fails in configfs_create(), this can make the racing
> rmdir() fail despite the concerned directory having no user-created entry (resp.
> no symlink pointing to it or one of its default groups) in the end.
> If this behavior is found unacceptable, I'll submit a fix in the same spirit as
> the racing mkdir() fix.
Ahh, but you can't wait on the mutex like you do in mkdir(),
because they're not ordered - it can race rename again.
Joel
--
Dort wo man B?cher verbrennt, verbrennt man am Ende auch Mensch.
(Wherever they burn books, they will also end up burning people.)
- Heinrich Heine
Joel Becker
Principal Software Developer
Oracle
E-mail: [email protected]
Phone: (650) 506-8127
On Mon, Jun 16, 2008 at 03:29:00PM -0700, Joel Becker wrote:
> On Mon, Jun 16, 2008 at 08:09:11PM +0200, Louis Rilling wrote:
> > This patch introduces a similar (weird?) behavior as with mkdir failures making
> > rmdir fail: if symlink() races with rmdir() of the parent directory (or its
> > youngest user-created ancestor if parent is a default group) or rmdir() of the
> > target directory, and then fails in configfs_create(), this can make the racing
> > rmdir() fail despite the concerned directory having no user-created entry (resp.
> > no symlink pointing to it or one of its default groups) in the end.
> > If this behavior is found unacceptable, I'll submit a fix in the same spirit as
> > the racing mkdir() fix.
>
> Ahh, but you can't wait on the mutex like you do in mkdir(),
> because they're not ordered - it can race rename again.
Yes I can. In the mkdir() case, rmdir() waits on the mutex of one of the default
groups. The symlink case will be handled the same. The difference is that while
mkdir() tags the parent with CONFIGFS_USET_IN_MKDIR, symlink() will tag both the
parent and the target with CONFIGFS_USET_IN_SYMLINK. [ We can actually merge the
two flags in something like CONFIGFS_USET_ATTACHING. ] Since tagging requires
only to take configfs_dirent_lock, there will be no deadlock.
I'll send a patch later.
Louis
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
On Tue, Jun 17, 2008 at 12:42:59PM +0200, Louis Rilling wrote:
> On Mon, Jun 16, 2008 at 03:29:00PM -0700, Joel Becker wrote:
> > On Mon, Jun 16, 2008 at 08:09:11PM +0200, Louis Rilling wrote:
> > > This patch introduces a similar (weird?) behavior as with mkdir failures making
> > > rmdir fail: if symlink() races with rmdir() of the parent directory (or its
> > > youngest user-created ancestor if parent is a default group) or rmdir() of the
> > > target directory, and then fails in configfs_create(), this can make the racing
> > > rmdir() fail despite the concerned directory having no user-created entry (resp.
> > > no symlink pointing to it or one of its default groups) in the end.
> > > If this behavior is found unacceptable, I'll submit a fix in the same spirit as
> > > the racing mkdir() fix.
> >
> > Ahh, but you can't wait on the mutex like you do in mkdir(),
> > because they're not ordered - it can race rename again.
>
> Yes I can. In the mkdir() case, rmdir() waits on the mutex of one of the default
> groups. The symlink case will be handled the same. The difference is that while
> mkdir() tags the parent with CONFIGFS_USET_IN_MKDIR, symlink() will tag both the
> parent and the target with CONFIGFS_USET_IN_SYMLINK. [ We can actually merge the
> two flags in something like CONFIGFS_USET_ATTACHING. ] Since tagging requires
> only to take configfs_dirent_lock, there will be no deadlock.
Hm, you were right, sorry. We can only solve the race with rmdir() removing the
item where the symlink is created. For the target item, I don't know yet...
Louis
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes