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  • [parent not found: <CA+55aFznQaOWoSMNphgGJJWZ=8-odrc0DAUMzfGPQe+_N4UgNA@mail.gmail.com>]
  • * Re: skb_splice_bits() and large chunks in pipe (was Re: xfs_file_splice_read: possible circular locking dependency detected
      2016-09-18 22:31                             ` Al Viro
    @ 2016-09-19  0:22 Al Viro
      2016-09-20  9:51 ` Herbert Xu
      0 siblings, 1 reply; 101+ messages in thread
    From: Al Viro @ 2016-09-19  0:22 UTC (permalink / raw)
      To: Linus Torvalds
      Cc: Jens Axboe, Nick Piggin, linux-fsdevel, Network Development,
    	Eric Dumazet
    
    On Sun, Sep 18, 2016 at 11:31:17PM +0100, Al Viro wrote:
    
    > At the moment there are 11 callers (10 in mainline; one more added in
    > conversion of vmsplice_to_pipe() to new pipe locking, but it's irrelevant
    > anyway - it gets fed an iovec-backed iov_iter).  I'm looking through those
    > right now, hopefully will come up with something sane...
    
    FWIW, I wonder how many of those users are ready to cope with compound
    pages in the first place; they end up passed to
    	* skb_fill_page_desc().  Probably OK (as in all of them, modulo
    calculating the number of pages and ranges for them).
    	* shoved into scatterlist, which gets passed to virtqueue_add_sgs().
    Need to check virtio to see what happens there.
    	* shoved into nfs ->wb_page and fed into nfs_pageio_add_request() and
    machinery behind it.  These, BTW, are reachable by pipe_buffer-derived ones
    at the moment (splice to O_DIRECT nfs file).  The code looks like it's
    playing fast and loose with ->wb_page - in some cases it's an NFS pagecache
    one, in some - anything from userland, and there are places like
    	inode = page_file_mapping(req->wb_page)->host;
    which will do nasty things if they are ever reached by the second kind.
    nfs_pgio_rpcsetup() looks like it won't be happy with compound pages, but
    again, I'm not familiar enough with that code to tell if it's reachable
    from nfs_pageio_add_request().
    	* shoved into scatterlist, which gets fed into crypto/*.c machinery.
    No way for a pipe_buffer stuff to get there, fortunately, because I would
    be very surprised if it works correctly with compound pages and large
    ranges in those.
    	* shoved into lustre ->ldp_pages; almost certainly not ready for
    compound pages.
    	* fed to ceph_osd_data_pages_init(); again, practically certain not
    to be ready.
    	* put into dio_submit ->pages[], eventually fed to bio_add_page();
    that might be fixable, but it would take some massage in fs/direct-io.c
    	*�fuse - probably OK, but that's only on a fairly cursory look.
    
    It certainly won't be easy to verify in details ;-/
    
    ^ permalink raw reply	[flat|nested] 101+ messages in thread

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    2016-09-18  5:33                   ` xfs_file_splice_read: possible circular locking dependency detected Al Viro
    2016-09-19  3:08                     ` Nicholas Piggin
    2016-09-19  6:11                       ` Al Viro
    2016-09-19  7:26                         ` Nicholas Piggin
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         [not found]                       ` <20160917190023.GA8039@ZenIV.linux.org.uk>
    2016-09-18 19:31                         ` skb_splice_bits() and large chunks in pipe (was " Al Viro
    2016-09-18 20:12                           ` Linus Torvalds
    2016-09-18 22:31                             ` Al Viro
    2016-09-19  0:18                               ` Linus Torvalds
    2016-09-23 19:00                         ` [RFC][CFT] splice_read reworked Al Viro
    2016-09-23 19:01                           ` [PATCH 01/11] fix memory leaks in tracing_buffers_splice_read() Al Viro
    2016-09-23 19:02                           ` [PATCH 02/11] splice_to_pipe(): don't open-code wakeup_pipe_readers() Al Viro
    2016-09-23 19:02                           ` [PATCH 03/11] splice: switch get_iovec_page_array() to iov_iter Al Viro
    2016-09-23 19:03                           ` [PATCH 04/11] splice: lift pipe_lock out of splice_to_pipe() Al Viro
    2016-09-23 19:45                             ` Linus Torvalds
    2016-09-23 20:10                               ` Al Viro
    2016-09-23 20:36                                 ` Linus Torvalds
    2016-09-24  3:59                                   ` Al Viro
    2016-09-24 17:29                                     ` Al Viro
    2016-09-27 15:38                                       ` Nicholas Piggin
    2016-09-27 15:53                                       ` Chuck Lever
    2016-09-24  3:59                                   ` [PATCH 04/12] " Al Viro
    2016-09-26 13:35                                     ` Miklos Szeredi
    2016-09-27  4:14                                       ` Al Viro
    2016-12-17 19:54                                     ` Andreas Schwab
    2016-12-18 19:28                                       ` Linus Torvalds
    2016-12-18 19:57                                         ` Andreas Schwab
    2016-12-18 20:12                                         ` Al Viro
    2016-12-18 20:30                                           ` Al Viro
    2016-12-18 22:10                                             ` Linus Torvalds
    2016-12-18 22:18                                               ` Al Viro
    2016-12-18 22:22                                                 ` Linus Torvalds
    2016-12-18 22:49                                               ` Andreas Schwab
    2016-12-21 18:56                                               ` Andreas Schwab
    2016-12-21 19:12                                                 ` Linus Torvalds
    2016-09-24  4:00                                   ` [PATCH 06/12] new helper: add_to_pipe() Al Viro
    2016-09-26 13:49                                     ` Miklos Szeredi
    2016-09-24  4:01                                   ` [PATCH 10/12] new iov_iter flavour: pipe-backed Al Viro
    2016-09-29 20:53                                     ` Miklos Szeredi
    2016-09-29 22:50                                       ` Al Viro
    2016-09-30  7:30                                         ` Miklos Szeredi
    2016-10-03  3:34                                           ` [RFC] O_DIRECT vs EFAULT (was Re: [PATCH 10/12] new iov_iter flavour: pipe-backed) Al Viro
    2016-10-03 17:07                                             ` Linus Torvalds
    2016-10-03 18:54                                               ` Al Viro
    2016-09-24  4:01                                   ` [PATCH 11/12] switch generic_file_splice_read() to use of ->read_iter() Al Viro
    2016-09-24  4:02                                   ` [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Al Viro
    2016-09-23 19:03                           ` [PATCH 05/11] skb_splice_bits(): get rid of callback Al Viro
    2016-09-23 19:04                           ` [PATCH 06/11] new helper: add_to_pipe() Al Viro
    2016-09-23 19:04                           ` [PATCH 07/11] fuse_dev_splice_read(): switch to add_to_pipe() Al Viro
    2016-09-23 19:06                           ` [PATCH 08/11] cifs: don't use memcpy() to copy struct iov_iter Al Viro
    2016-09-23 19:08                           ` [PATCH 09/11] fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter() Al Viro
    2016-09-26  9:31                             ` Miklos Szeredi
    2016-09-23 19:09                           ` [PATCH 10/11] new iov_iter flavour: pipe-backed Al Viro
    2016-09-23 19:10                           ` [PATCH 11/11] switch generic_file_splice_read() to use of ->read_iter() Al Viro
    2016-09-30 13:32                           ` [RFC][CFT] splice_read reworked CAI Qian
    2016-09-30 17:42                             ` CAI Qian
    2016-09-30 18:33                               ` CAI Qian
    2016-10-03  1:37                                 ` Al Viro
    2016-10-03 17:49                                   ` CAI Qian
    2016-10-04 17:39                                     ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) CAI Qian
    2016-10-04 21:42                                       ` tj
    2016-10-05 14:09                                         ` CAI Qian
    2016-10-05 15:30                                           ` tj
    2016-10-05 15:54                                             ` CAI Qian
    2016-10-05 18:57                                               ` CAI Qian
    2016-10-05 20:05                                                 ` Al Viro
    2016-10-06 12:20                                                   ` CAI Qian
    2016-10-06 12:25                                                     ` CAI Qian
    2016-10-06 16:11                                                       ` CAI Qian
    2016-10-06 17:00                                                         ` Linus Torvalds
    2016-10-06 18:12                                                           ` CAI Qian
    2016-10-07  9:57                                                           ` Dave Chinner
    2016-10-07 15:25                                                             ` Linus Torvalds
    2016-10-07  7:08                                                       ` Jan Kara
    2016-10-07 14:43                                                         ` CAI Qian
    2016-10-07 15:27                                                           ` CAI Qian
    2016-10-07 18:56                                                             ` CAI Qian
    2016-10-09 21:54                                                               ` Dave Chinner
    2016-10-10 14:10                                                                 ` CAI Qian
    2016-10-10 20:14                                                                   ` CAI Qian
    2016-10-10 21:57                                                                   ` Dave Chinner
    2016-10-12 19:50                                                                     ` [bisected] " CAI Qian
    2016-10-12 20:59                                                                       ` Dave Chinner
    2016-10-13 16:25                                                                         ` CAI Qian
    2016-10-13 20:49                                                                           ` Dave Chinner
    2016-10-13 20:56                                                                             ` CAI Qian
    2016-10-09 21:51                                                           ` Dave Chinner
    2016-10-21 15:38                                                         ` [4.9-rc1+] overlayfs lockdep CAI Qian
    2016-10-24 12:57                                                           ` Miklos Szeredi
    2016-10-07  9:27                                                     ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) Dave Chinner
    2016-10-03  1:42                               ` [RFC][CFT] splice_read reworked Al Viro
    2016-10-03 14:06                                 ` CAI Qian
    2016-10-03 15:20                                   ` CAI Qian
    2016-10-03 21:12                                     ` Dave Chinner
    2016-10-04 13:57                                       ` CAI Qian
    2016-10-03 20:32                                   ` CAI Qian
    2016-10-03 20:35                                     ` Al Viro
    2016-10-04 13:29                                       ` CAI Qian
    2016-10-04 14:28                                         ` Al Viro
    2016-10-04 16:21                                           ` CAI Qian
    2016-10-04 20:12                                             ` Al Viro
    2016-10-05 14:30                                               ` CAI Qian
    2016-10-05 16:07                                                 ` Al Viro
    2016-09-19  0:22 skb_splice_bits() and large chunks in pipe (was Re: xfs_file_splice_read: possible circular locking dependency detected Al Viro
    2016-09-20  9:51 ` Herbert Xu
    

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