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Date: Wed, 25 Apr 2012 11:28:58 -0400 From: "J. Bruce Fields" <bfields@...ldses.org> To: Al Viro <viro@...IV.linux.org.uk> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, "J. Bruce Fields" <bfields@...hat.com> Subject: Re: [PATCH 5/5] vfs: change nondirectory i_mutex ordering to fix quota deadlock On Wed, Apr 25, 2012 at 11:22:09AM -0400, bfields@...ldses.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? > + > /** > * lock_two_nondirectories - take two i_mutexes on non-directory objects > * @inode1: first inode to lock; must be non-NULL > @@ -970,7 +981,7 @@ void lock_two_nondirectories(struct inode *inode1, struct inode *inode2) > { > if (inode1 == inode2 || inode2 == NULL) > mutex_lock(&inode1->i_mutex); > - else if (inode1 < inode2) { > + else if (nondir_mutex_ordered(inode1, inode2)) { > mutex_lock(&inode1->i_mutex); > mutex_lock_nested(&inode2->i_mutex, I_MUTEX_QUOTA); But I still don't see how to stop this code racing with S_NOQUOTA being toggled. --b. > > -- > 1.7.5.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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