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    SubjectRe: [PATCH 5/5] vfs: change nondirectory i_mutex ordering to fix quota deadlock
    On Wed 25-04-12 11:28:58, J. Bruce Fields wrote:
    > On Wed, Apr 25, 2012 at 11:22:09AM -0400, bfields@fieldses.org wrote:
    > > diff --git a/fs/inode.c b/fs/inode.c
    > > index 487c924..13d23b6 100644
    > > --- a/fs/inode.c
    > > +++ b/fs/inode.c
    > > @@ -961,6 +961,17 @@ void unlock_new_inode(struct inode *inode)
    > > }
    > > EXPORT_SYMBOL(unlock_new_inode);
    > >
    > > +/*
    > > + * We order !IS_NOQUOTA files before ISNOQUOTA files, and by pointer
    > > + * within each category.
    > > + */
    > > +static bool nondir_mutex_ordered(struct inode *inode1, struct inode *inode2)
    > > +{
    > > + if (IS_NOQUOTA(inode1) == IS_NOQUOTA(inode2))
    > > + return inode1 < inode2;
    > > + return IS_NOQUOTA(inode2);
    > > +}
    >
    > This seems kind of awful. Is it what you were thinking of originally,
    > Al, and could we live with it?
    Yeah, it's pretty ugly and also racy. I'm just now testing patches that
    would get rid of I_MUTEX_QUOTA usage for filesystems (except GFS2) and
    quota code. GFS2 could be certainly dealt with as well (at least by
    introducing a new GFS2 internal lock) so this ugly code can go away.

    Honza



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