On Thu, Mar 22, 2012 at 05:19:09PM +0200, Kasatkin, Dmitry wrote: > On Thu, Mar 22, 2012 at 5:09 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Mar 22, 2012 at 10:53:04AM -0400, Mimi Zohar wrote: > >> > BTW, you've missed several other places in mm/* doing fput(), so it wouldn't > >> > be enough to paper over your problem anyway. > >> > > >> > Final fput() *can* happen under mmap_sem. ??Period. > >> > >> I think I got that loud and clear; otherwise we wouldn't have come up > >> with deferring the __fput(). ??We have a very real problem here - writing > >> extended attributes requires taking the i_mutex. > > > > Don't do it, then? ??If you _must_ write to xattr on final fput, I'd suggest > > starting to figure out if xattr needs its protection to be ->i_mutex - it > > might make sense to introduce a separate mutex for xattr crap. ??Or not - I'm > > "Or not" ... How to understand you? "Or it might not make sense to go that way" > > not familiar enough with the guts of xattr handling in individual filesystems > > to tell if that would work (e.g. if it would need unpleasant changes to > > ->setattr() instances)... IOW, you'll need to do quite a bit of code review to tell if it's a feasible direction or not - I can't tell without doing the same amount of RTFS; look for the places where xattrs are modified by fs code, see how far is ->i_mutex acquired, whether xattrs are read in the same section and whether we rely on ->i_mutex to keep the xattr values unchanged between two reads or write and read... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
