Re: next-20140707 - crash during cryptsetup.

[Valdis Kletnieks]

System died a horrid death when cryptsetup was trying to get an encrypted
disk up and running.

Bisected down to this commit, and vanilla next-20140714 crashes the same way,
but  boots fine with this single commit reverted:

commit 254c4407cb84a6dec90336054615b0f0e996bb7c
Author: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Date:   Tue Jul 1 10:55:15 2014 -0600

    bio: modify __bio_add_page() to accept pages that don't start a new segment

    The original behaviour is to refuse to add a new page if the maximum
    number of segments has been reached, regardless of the fact the page we
    are going to add can be merged into the last segment or not.

    Unfortunately, when the system runs under heavy memory fragmentation
    conditions, a driver may try to add multiple pages to the last segment.
    The original code won't accept them and EBUSY will be reported to
    userspace.

    This patch modifies the function so it refuses to add a page only in case
    the latter starts a new segment and the maximum number of segments has
    already been reached.


[   25.929846] ------------[ cut here ]------------
[   25.929873] kernel BUG at fs/direct-io.c:747!
[   25.929893] invalid opcode: 0000 [#1] PREEMPT SMP
[   25.929922] Modules linked in:
[   25.929940] CPU: 3 PID: 308 Comm: systemd-cryptse Not tainted 3.16.0-rc4-next-20140707 #247
[   25.929974] Hardware name: Dell Inc. Latitude E6530/07Y85M, BIOS A14 01/13/2014
[   25.930004] task: ffff880222609e50 ti: ffff8802225b4000 task.ti: ffff8802225b4000
[   25.930034] RIP: 0010:[<ffffffff8116bee5>]  [<ffffffff8116bee5>] dio_send_cur_page+0xd7/0xe3
[   25.930074] RSP: 0018:ffff8802225b7aa0  EFLAGS: 00010202
[   25.930096] RAX: 0000000000000001 RBX: ffff8802225b7c01 RCX: 0000000000000000
[   25.930126] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff81d13cf0
[   25.930155] RBP: ffff8802225b7ac8 R08: 0000000000000000 R09: 0000000000000001
[   25.930184] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800c6e8dc00
[   25.930213] R13: ffff8802225b7bc0 R14: 000000000000007a R15: 000000000000007c
[   25.930243] FS:  00007f5908c49840(0000) GS:ffff88022dd80000(0000) knlGS:0000000000000000
[   25.930276] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   25.930300] CR2: 00000000006ecf18 CR3: 0000000222bb1000 CR4: 00000000001407e0
[   25.930329] Stack:
[   25.930339]  0000000100000000 ffff8800c6e8dc00 ffffea0002ba9d68 0000000000000800
[   25.930380]  ffff8802225b7c28 ffff8802225b7b08 ffffffff8116bfa2 0000000022110780
[   25.930419]  ffff8800c6e8dc00 ffffea0002ba9d68 0000000000000800 0000000000000001
[   25.930458] Call Trace:
[   25.930473]  [<ffffffff8116bfa2>] submit_page_section+0xb1/0x114
[   25.930499]  [<ffffffff8116cad6>] do_blockdev_direct_IO+0xa28/0xd1f
[   25.930527]  [<ffffffff81169558>] ? I_BDEV+0xd/0xd
[   25.930549]  [<ffffffff8116cdfc>] __blockdev_direct_IO+0x2f/0x31
[   25.930575]  [<ffffffff8116cdfc>] ? __blockdev_direct_IO+0x2f/0x31
[   25.930601]  [<ffffffff81169558>] ? I_BDEV+0xd/0xd
[   25.930622]  [<ffffffff811698e2>] blkdev_direct_IO+0x2e/0x30
[   25.930647]  [<ffffffff81169558>] ? I_BDEV+0xd/0xd
[   25.930669]  [<ffffffff810f314c>] generic_file_read_iter+0x93/0x5c8
[   25.930697]  [<ffffffff81169c8a>] blkdev_read_iter+0x35/0x37
[   25.930722]  [<ffffffff81139725>] new_sync_read+0x74/0x98
[   25.930746]  [<ffffffff81139e0c>] vfs_read+0xce/0x124
[   25.930768]  [<ffffffff8113a665>] SyS_read+0x4b/0x79
[   25.930791]  [<ffffffff8167ea92>] system_call_fastpath+0x16/0x1b
[   25.930816] Code: fe ff ff 48 89 df e8 40 fe ff ff 48 c7 c7 f0 3c d1 81 85 c0 89 45 dc 0f 95 c3 31 d2 0f b6 f3 e8 4f ad f6 ff 84 db 8b 45 dc 74 02 <0f> 0b 5a 5b 41 5c 41 5d 41 5e 5d c3 55 48 89 e5 41 57 4d 89 cf
[   25.931060] RIP  [<ffffffff8116bee5>] dio_send_cur_page+0xd7/0xe3
[   25.931088]  RSP <ffff8802225b7aa0>
[   25.931132] ---[ end trace 5bdcfa6254e32464 ]---

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