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Message-ID: <1291063531.3248.30.camel@localhost.localdomain> Date: Mon, 29 Nov 2010 15:45:31 -0500 From: Eric Paris <eparis@...hat.com> To: Lino Sanfilippo <LinoSanfilippo@....de> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: [PATCH] fanotify: dont destroy mark when ignore mask is cleared On Wed, 2010-11-24 at 13:31 +0100, Lino Sanfilippo wrote: > 2. I just realized that we cant simply call destroy_mark() if the masks are 0. > There may be one or more concurrent processes calling fsnotify_find_inode_mark() > (see fanotify_add_inode_mark()) and get the mark we are about to destroy at the > same time. > > I will take a closer look at it, but it seems to be difficult to me to safely > call destroy_mark() as long as we are not in the context of fanotify_release() (in > which we dont have to deal with concurrency like that any more). I guess it is a question of safe vs racy. Yes it is safe, nothing will explode or panic. But we might have a race between one task removing an event type causing the mask to go to 0 and we should destroy the mark and another task adding an event type. If it raced just right we might destroy the mark after the second task added to it. I guess we really need to serialize fsnotify_mark() per group to solve the race... Do you want to take a stab at fixing these things or should I? -Eric -- 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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