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    SubjectRe: freeze vs freezer
    Date
    On Thursday, 22 of November 2007, Jeremy Fitzhardinge wrote:
    > It seems that a process blocked in a write to an xfs filesystem due to
    > xfs_freeze cannot be frozen by the freezer.

    The freezer doesn't handle tasks in TASK_UNINTERRUPTIBLE and I don't know how
    to make it handle them without at least partially defeating its purpose.

    > I see this if I suspend my laptop while doing something xfs-filesystem
    > intensive, like a kernel build. My suspend scripts freeze the XFS
    > filesystem (as Dave said I should), which presumably blocks some writer,
    > and then the freezer times out and fails to complete.
    >
    > Here's part of the process dump the freezer does when it times out:
    >
    > cc1 D 00000000 0 18138 18137
    > dd5f1e24 00200082 00000002 00000000 ecdeeb00 ecdeec64 c200f280 00000001
    > 009c09a0 dd5f1e0c dd5f1e0c 0000000f 00000000 00000000 00000000 dd5f1e74
    > c7beb480 dd5f1e88 dd5f1ea8 c0228d97 e8889540 dd5f1e38 c015b75d dd5f1e44
    > Call Trace:
    > [<c0228d97>] xfs_write+0xf4/0x6d9
    > [<c0226038>] xfs_file_aio_write+0x53/0x5b
    > [<c0171c15>] do_sync_write+0xae/0xec
    > [<c0172343>] vfs_write+0xa4/0x120
    > [<c01728d7>] sys_write+0x3b/0x60
    > [<c0106fae>] sysenter_past_esp+0x6b/0xa1
    > =======================
    >
    >
    > I haven't looked at how to fix this yet. I only just worked out why I
    > was getting suspend failures.

    Well, you can add freezer_do_not_count()/freezer_count() annotations to
    xfs_write() (and whatever else is blocked as a result of the XFS being frozen).

    Generally, that would be risky without the freezing of XFS, however, because it
    might leak us filesystem data to a storage device after creating a hibernation
    image which would result in the filesystem corruption after the resume.

    Still, if you only suspend to RAM, that should be safe.

    Greetings,
    Rafael
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