On Fri, Jul 09, 2010 at 01:42:06PM +0300, Sergey Senozhatsky wrote: > On (07/09/10 05:16), Frederic Weisbecker wrote: > > On Sun, Jul 04, 2010 at 10:15:23AM +0100, Al Viro wrote: > > > On Sat, Jul 03, 2010 at 10:43:23AM +0100, Al Viro wrote: > > > > On Sat, Jul 03, 2010 at 10:24:42AM +0100, Al Viro wrote: > > > > > > > > > Gyah... For the 1001st time: readdir() is far from being the only thing that > > > > > nests mmap_sem inside i_mutex. In particular, write() does the same thing. > > > > > > > > > > So yes, it *is* a real deadlock, TYVM, with no directories involved. Open the > > > > > same file twice, mmap one fd, close it, then have munmap() hitting i_mutex > > > > > in reiserfs_file_release() race with write() through another fd. > > > > > > > > > > Incidentally, reiserfs_file_release() checks in the fastpath look completely > > > > > bogus. Checking i_count? What the hell is that one about? And no, these > > > > > checks won't stop open() coming between them and grabbing i_mutex, so they > > > > > couldn't prevent the deadlock in question anyway. > > > > > > > > ... and unfortunately it's been that way since the the initial merge in 2.4.early. > > > > FWIW, it seems that i_count check was a misguided attempt to check that no other > > > > opened struct file are there, but it's > > > > a) wrong, since way, _way_ back - open() affects d_count, not i_count > > > > b) wrong even with such modification (consider hardlinks) > > > > c) wrong for even more reasons since forever - i_count and d_count could > > > > be bumped by many things at any time > > > > d) hopelessly racy anyway, since another open() could very well have > > > > happened just as we'd finished these checks. > > > > > > OK... See 22093b8f3d387f77 in vfs-2.6.git for-next (should propagate to > > > git.kernel.org shortly). That ought to deal with this crap, assuming I hadn't > > > fucked up somewhere... > > > > > > Looks good. Thanks for fixing this! > > > > Seems to work fine with my test app. > > Reported-by/Tested-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Great! -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
