Messages in this thread | | | Subject | Re: [RFC][PATCH] inotify kernel api | From | John McCutchan <> | Date | Mon, 10 Apr 2006 14:36:28 -0400 |
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On Thu, 2006-04-06 at 13:06 -0400, Amy Griffis wrote: > The following patch against 2.6.17-rc1-mm1 introduces a kernel API for inotify. > > Event processing is unchanged except for the indirection added for the > callback. In inotify_user.c, an additional per-device mutex is held > while adding watches to prevent adding the same watch twice. The > design retains the original assumption that there will be more watches > per inotify_handle than watches on any given inode, and performs the > search for existing watches accordingly. >
Why do we need the 'up_mutex' mutex? Was this a bug in the old code?
> This patch makes the inotify_watch public so it can be embedded in callers' own > watch structures, which avoids the use of a void ptr to caller data. > Even though inotify_watch is public, callers must use the established > interfaces to access inotify_watch contents. Was this the best > choice? >
I suppose this is an alright change. As long as it is understood that there is no guarantee about the layout of the inotify_watch structure. A comment in inotify.h should do.
> I think the locking may be less than ideal, as the > inode->inotify_mutex must be held to traverse the inode's watchlist, > and thus must be held during the callback. The result is that the > caller can't hold any locks taken during callback processing while > calling any of the published inotify interfaces, making > synchronization a little more difficult. >
Well, I think it's up for the kernel consumers to decide whether or not this is acceptable. It's probably a good idea to come up with some use cases for the kernel API and see if this _is_ a problem. Since the callbacks will be run inside the VFS ops, they need to be small and fast, so they probably should just be putting the event on a list and handling it later.
Looking over the patch, nothing jumps out at me as being wrong. But some stress testing would convince me faster than my eyes can.
-- John McCutchan <john@johnmccutchan.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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