From: ebiederm@xmission.com (Eric W. Biederman) To: Davide Libenzi <davidel@xmailserver.org> Cc: Al Viro <viro@ZenIV.linux.org.uk>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins <hugh@veritas.com>, Tejun Heo <tj@kernel.org>, Alexey Dobriyan <adobriyan@gmail.com>, Linus Torvalds <torvalds@linux-foundation.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>, Greg Kroah-Hartman <gregkh@suse.de>, Nick Piggin <npiggin@suse.de>, Andrew Morton <akpm@linux-foundation.org>, Christoph Hellwig <hch@infradead.org>, "Eric W. Biederman" <ebiederm@maxwell.aristanetworks.com>, "Eric W. Biederman" <ebiederm@aristanetworks.com> Subject: Re: [PATCH 18/23] vfs: Teach epoll to use file_hotplug_lock Date: Tue, 02 Jun 2009 14:23:47 -0700 [thread overview] Message-ID: <m1eiu2qqho.fsf@fess.ebiederm.org> (raw) In-Reply-To: <alpine.DEB.1.10.0906020944540.12866@makko.or.mcafeemobile.com> (Davide Libenzi's message of "Tue\, 2 Jun 2009 09\:51\:42 -0700 \(PDT\)") Davide Libenzi <davidel@xmailserver.org> writes: > On Mon, 1 Jun 2009, Eric W. Biederman wrote: > >> From: Eric W. Biederman <ebiederm@maxwell.aristanetworks.com> >> >> Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com> >> --- >> fs/eventpoll.c | 39 ++++++++++++++++++++++++++++++++------- >> 1 files changed, 32 insertions(+), 7 deletions(-) > > This patchset gives me the willies for the amount of changes and possible > impact on many subsystems. It both is and is not that bad. It is the cost of adding a lock. For the VFS except for nfsd the I have touched everything that needs to be touched. Other subsystems that open read/write close files should be able to use existing vfs helpers so they don't need to know about the new locking explicitly. Actually taking advantage of this infrastructure in a subsystem is comparatively easy. It took me about an hour to get uio using it. That part is not deep by any means and is opt in. > Without having looked at the details, are you aware that epoll does not > act like poll/select, and fds are not automatically removed (as in, > dequeued from the poll wait queue) in any foreseeable amount of time after > a POLLERR is received? Yes I am aware of how epoll acts differently. > As far as the usespace API goes, they have the right to remain there. I absolutely agree. Currently I have the code acting like close() with respect to epoll and just having the file descriptor vanish at the end of the revoke. While we the revoke is in progress you get an EIO. The file descriptor is not freed by a revoke operation so you can happily hang unto it as long as you want. I thought of doing something more uniform to user space. But I observed that the existing epoll punts on the case of a file descriptor being closed and locking to go from a file to the other epoll datastructures is pretty horrid I said forget it and used the existing close behaviour. Eric
WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman) To: Davide Libenzi <davidel@xmailserver.org> Cc: Al Viro <viro@ZenIV.linux.org.uk>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins <hugh@veritas.com>, Tejun Heo <tj@kernel.org>, Alexey Dobriyan <adobriyan@gmail.com>, Linus Torvalds <torvalds@linux-foundation.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>, Greg Kroah-Hartman <gregkh@suse.de>, Nick Piggin <npiggin@suse.de>, Andrew Morton <akpm@linux-foundation.org>, Christoph Hellwig <hch@infradead.org>, "Eric W. Biederman" <ebiederm@maxwell.aristanetworks.com>, "Eric W. Biederman" <ebiederm@aristanetworks.com> Subject: Re: [PATCH 18/23] vfs: Teach epoll to use file_hotplug_lock Date: Tue, 02 Jun 2009 14:23:47 -0700 [thread overview] Message-ID: <m1eiu2qqho.fsf@fess.ebiederm.org> (raw) In-Reply-To: <alpine.DEB.1.10.0906020944540.12866@makko.or.mcafeemobile.com> (Davide Libenzi's message of "Tue\, 2 Jun 2009 09\:51\:42 -0700 \(PDT\)") Davide Libenzi <davidel@xmailserver.org> writes: > On Mon, 1 Jun 2009, Eric W. Biederman wrote: > >> From: Eric W. Biederman <ebiederm@maxwell.aristanetworks.com> >> >> Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com> >> --- >> fs/eventpoll.c | 39 ++++++++++++++++++++++++++++++++------- >> 1 files changed, 32 insertions(+), 7 deletions(-) > > This patchset gives me the willies for the amount of changes and possible > impact on many subsystems. It both is and is not that bad. It is the cost of adding a lock. For the VFS except for nfsd the I have touched everything that needs to be touched. Other subsystems that open read/write close files should be able to use existing vfs helpers so they don't need to know about the new locking explicitly. Actually taking advantage of this infrastructure in a subsystem is comparatively easy. It took me about an hour to get uio using it. That part is not deep by any means and is opt in. > Without having looked at the details, are you aware that epoll does not > act like poll/select, and fds are not automatically removed (as in, > dequeued from the poll wait queue) in any foreseeable amount of time after > a POLLERR is received? Yes I am aware of how epoll acts differently. > As far as the usespace API goes, they have the right to remain there. I absolutely agree. Currently I have the code acting like close() with respect to epoll and just having the file descriptor vanish at the end of the revoke. While we the revoke is in progress you get an EIO. The file descriptor is not freed by a revoke operation so you can happily hang unto it as long as you want. I thought of doing something more uniform to user space. But I observed that the existing epoll punts on the case of a file descriptor being closed and locking to go from a file to the other epoll datastructures is pretty horrid I said forget it and used the existing close behaviour. Eric -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2009-06-02 21:24 UTC|newest] Thread overview: 207+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-04-11 12:01 [RFC][PATCH 0/9] File descriptor hot-unplug support Eric W. Biederman 2009-04-11 12:01 ` Eric W. Biederman 2009-04-11 12:03 ` [RFC][PATCH 1/9] mm: Introduce remap_file_mappings Eric W. Biederman 2009-04-11 12:03 ` Eric W. Biederman 2009-04-11 12:05 ` [RFC][PATCH 2/9] mm: Implement generic support for revoking a mapping Eric W. Biederman 2009-04-11 12:05 ` Eric W. Biederman 2009-04-11 12:05 ` Eric W. Biederman 2009-04-11 12:06 ` [RFC][PATCH 3/9] sysfs: Use remap_file_mappings Eric W. Biederman 2009-04-11 12:06 ` Eric W. Biederman 2009-04-11 12:06 ` Eric W. Biederman 2009-04-11 12:07 ` [RFC][PATCH 4/9] vfs: Generalize the file_list Eric W. Biederman 2009-04-11 12:07 ` Eric W. Biederman 2009-04-11 12:07 ` Eric W. Biederman 2009-04-11 12:08 ` [RFC][PATCH 5/9] vfs: Introduce basic infrastructure for revoking a file Eric W. Biederman 2009-04-11 12:08 ` Eric W. Biederman 2009-04-11 12:08 ` Eric W. Biederman 2009-04-14 22:12 ` Jonathan Corbet 2009-04-14 22:12 ` Jonathan Corbet 2009-04-15 2:55 ` Eric W. Biederman 2009-04-15 2:55 ` Eric W. Biederman 2009-04-15 2:55 ` Eric W. Biederman 2009-04-11 12:10 ` [RFC][PATCH 6/9] vfs: Utilize fops_read_lock where appropriate Eric W. Biederman 2009-04-11 12:10 ` Eric W. Biederman 2009-04-11 12:10 ` Eric W. Biederman 2009-04-11 12:11 ` [RFC][PATCH 7/9] vfs: Optimize fops_read_lock Eric W. Biederman 2009-04-11 12:11 ` Eric W. Biederman 2009-04-11 12:11 ` Eric W. Biederman 2009-04-11 12:13 ` [RFC][PATCH 8/9] vfs: Implement generic revoked file operations Eric W. Biederman 2009-04-11 12:13 ` Eric W. Biederman 2009-04-11 12:13 ` Eric W. Biederman 2009-04-12 18:56 ` Jamie Lokier 2009-04-12 18:56 ` Jamie Lokier 2009-04-12 20:04 ` Eric W. Biederman 2009-04-12 20:04 ` Eric W. Biederman 2009-04-12 20:31 ` Jamie Lokier 2009-04-12 20:31 ` Jamie Lokier 2009-04-12 21:53 ` Eric W. Biederman 2009-04-12 21:53 ` Eric W. Biederman 2009-04-12 20:54 ` Eric W. Biederman 2009-04-12 20:54 ` Eric W. Biederman 2009-04-12 21:02 ` Jamie Lokier 2009-04-12 21:02 ` Jamie Lokier 2009-04-12 23:06 ` Eric W. Biederman 2009-04-12 23:06 ` Eric W. Biederman 2009-04-11 12:14 ` [RFC][PATCH 9/9] proc: Use the generic vfs revoke facility that now exists Eric W. Biederman 2009-04-11 12:14 ` Eric W. Biederman 2009-04-11 15:58 ` [RFC][PATCH 0/9] File descriptor hot-unplug support Al Viro 2009-04-11 15:58 ` Al Viro 2009-04-11 16:49 ` Eric W. Biederman 2009-04-11 16:49 ` Eric W. Biederman 2009-04-11 16:56 ` Al Viro 2009-04-11 16:56 ` Al Viro 2009-04-11 23:57 ` Eric W. Biederman 2009-04-11 23:57 ` Eric W. Biederman 2009-04-12 20:21 ` Eric W. Biederman 2009-04-12 20:21 ` Eric W. Biederman 2009-04-14 3:16 ` Tejun Heo 2009-04-14 3:16 ` Tejun Heo 2009-04-14 7:39 ` Eric W. Biederman 2009-04-14 7:39 ` Eric W. Biederman 2009-04-14 7:45 ` Tejun Heo 2009-04-14 7:45 ` Tejun Heo 2009-04-14 8:27 ` Eric W. Biederman 2009-04-14 8:27 ` Eric W. Biederman 2009-04-14 8:49 ` Tejun Heo 2009-04-14 8:49 ` Tejun Heo 2009-04-14 15:07 ` Jamie Lokier 2009-04-14 15:07 ` Jamie Lokier 2009-04-14 19:09 ` Eric W. Biederman 2009-04-14 19:09 ` Eric W. Biederman 2009-06-01 21:45 ` [PATCH 0/23] File descriptor hot-unplug support v2 Eric W. Biederman 2009-06-01 21:45 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 01/23] mm: Introduce revoke_file_mappings Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 22:25 ` Andrew Morton 2009-06-01 22:25 ` Andrew Morton 2009-06-02 0:12 ` Eric W. Biederman 2009-06-02 0:12 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 02/23] vfs: Implement unpoll_file Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-06 8:08 ` Al Viro 2009-06-06 8:08 ` Al Viro 2009-06-01 21:50 ` [PATCH 03/23] vfs: Generalize the file_list Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-02 7:06 ` Nick Piggin 2009-06-02 7:06 ` Nick Piggin 2009-06-05 19:33 ` Eric W. Biederman 2009-06-05 19:33 ` Eric W. Biederman 2009-06-09 10:38 ` Nick Piggin 2009-06-09 10:38 ` Nick Piggin 2009-06-09 18:38 ` Eric W. Biederman 2009-06-09 18:38 ` Eric W. Biederman 2009-06-10 6:05 ` Nick Piggin 2009-06-10 6:05 ` Nick Piggin 2009-06-01 21:50 ` [PATCH 04/23] vfs: Introduce infrastructure for revoking a file Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-02 5:16 ` Pekka Enberg 2009-06-02 5:16 ` Pekka Enberg 2009-06-02 6:51 ` Eric W. Biederman 2009-06-02 6:51 ` Eric W. Biederman 2009-06-02 7:08 ` Pekka Enberg 2009-06-02 7:08 ` Pekka Enberg 2009-06-02 7:08 ` Pekka Enberg 2009-06-02 7:14 ` Nick Piggin 2009-06-02 7:14 ` Nick Piggin 2009-06-02 17:06 ` Linus Torvalds 2009-06-02 17:06 ` Linus Torvalds 2009-06-02 20:52 ` Eric W. Biederman 2009-06-02 20:52 ` Eric W. Biederman 2009-06-03 6:37 ` Nick Piggin 2009-06-03 6:37 ` Nick Piggin 2009-06-02 22:56 ` Eric W. Biederman 2009-06-02 22:56 ` Eric W. Biederman 2009-06-03 6:38 ` Nick Piggin 2009-06-03 6:38 ` Nick Piggin 2009-06-05 9:03 ` Miklos Szeredi 2009-06-05 9:03 ` Miklos Szeredi 2009-06-05 19:06 ` Eric W. Biederman 2009-06-05 19:06 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 05/23] vfs: Teach lseek to use file_hotplug_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 06/23] vfs: Teach read/write to use file_hotplug_read_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 07/23] vfs: Teach sendfile,splice,tee,and vmsplice to use file_hotplug_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-03 23:39 ` Badari Pulavarty 2009-06-03 23:39 ` Badari Pulavarty 2009-06-05 19:37 ` Eric W. Biederman 2009-06-05 19:37 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 08/23] vfs: Teach readdir " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 09/23] vfs: Teach poll and select " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 10/23] vfs: Teach do_path_lookup " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 11/23] mm: Teach mmap " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 12/23] vfs: Teach fcntl " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 13/23] vfs: Teach ioctl " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 14/23] vfs: Teach flock " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 15/23] vfs: Teach fallocate, and filp_close " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 16/23] vfs: Teach fstatfs, fstatfs64, ftruncate, fchdir, fchmod, fchown " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 17/23] proc: Teach /proc/<pid>/fd " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 18/23] vfs: Teach epoll " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-02 16:51 ` Davide Libenzi 2009-06-02 16:51 ` Davide Libenzi 2009-06-02 21:23 ` Eric W. Biederman [this message] 2009-06-02 21:23 ` Eric W. Biederman 2009-06-02 21:52 ` Davide Libenzi 2009-06-02 21:52 ` Davide Libenzi 2009-06-02 22:51 ` Eric W. Biederman 2009-06-02 22:51 ` Eric W. Biederman 2009-06-03 14:57 ` Davide Libenzi 2009-06-03 14:57 ` Davide Libenzi 2009-06-03 20:53 ` Eric W. Biederman 2009-06-03 20:53 ` Eric W. Biederman 2009-06-04 0:50 ` Davide Libenzi 2009-06-04 0:50 ` Davide Libenzi 2009-06-04 1:42 ` Eric W. Biederman 2009-06-04 1:42 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 19/23] eventpoll: Fix comment Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 20/23] vfs: Teach aio to use file_hotplug_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 21/23] vfs: Teach fsync " Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 22/23] vfs: Teach fadvice to file_hotplug_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-01 21:50 ` [PATCH 23/23] vfs: Teach readahead to use the file_hotplug_lock Eric W. Biederman 2009-06-01 21:50 ` Eric W. Biederman 2009-06-03 23:25 ` Badari Pulavarty 2009-06-03 23:25 ` Badari Pulavarty 2009-06-06 8:03 ` [PATCH 0/23] File descriptor hot-unplug support v2 Al Viro 2009-06-06 8:03 ` Al Viro 2009-06-08 9:41 ` Miklos Szeredi 2009-06-08 9:41 ` Miklos Szeredi 2009-06-08 10:24 ` Jamie Lokier 2009-06-08 10:24 ` Jamie Lokier 2009-06-08 16:29 ` Al Viro 2009-06-08 16:29 ` Al Viro 2009-06-08 16:44 ` Miklos Szeredi 2009-06-08 16:44 ` Miklos Szeredi 2009-06-08 17:50 ` Al Viro 2009-06-08 17:50 ` Al Viro 2009-06-08 18:01 ` Linus Torvalds 2009-06-08 18:01 ` Linus Torvalds 2009-06-08 18:50 ` Al Viro 2009-06-08 18:50 ` Al Viro 2009-06-08 19:18 ` Linus Torvalds 2009-06-08 19:18 ` Linus Torvalds 2009-06-09 6:42 ` Eric W. Biederman 2009-06-09 6:42 ` Eric W. Biederman 2009-06-09 10:52 ` Nick Piggin 2009-06-09 10:52 ` Nick Piggin 2009-06-09 5:50 ` Miklos Szeredi 2009-06-09 5:50 ` Miklos Szeredi 2009-06-09 6:31 ` Eric W. Biederman 2009-06-09 6:31 ` Eric W. Biederman 2009-06-09 6:22 ` Eric W. Biederman 2009-06-09 6:22 ` Eric W. Biederman
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