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    SubjectRe: strange sparc64 -> i586 intermittent but reproducible NFS write errors to one and only one fs
    [Large amount of quoting to provide useful context; see below.]

    On Fri, 10 Jan 2003, Denis Vlasenko recommended:
    > On 10 January 2003 00:56, Nix wrote:
    >> When I rebooted my systems into 2.4.20 (from 2.4.19), I started
    >> seeing EIO write() errors to files in my ext3 home directory
    >> (NFS-mounted, exported async).
    >> So I knocked up a test program (included below) to try to track the
    >> failing writes down, and got more confused.
    >> The properties of the failing writes that I've been able to determine
    >> thus far are as follows; look out, they're weird as hell:
    >> - the failures are definitely from write(), not open().
    >> - writes from sparc64 to one filesystem, and only one filesystem, on
    >> i586, both running 2.4.20, UDP NFSv3; rquotad and quotas are on,
    >> but I am well within my quota. (quota 3.06, nfs-utils 1.0). Writes to
    >> other filesystems on the same machine, even if they too are using
    >> ext3, even if they too have user quotas for the same user.
    >> What differs between filesystems that work and the one that fails
    >> I can't tell; other FSen *on the same block device* work... (the
    >> block device is an un-RAIDed SCSI disk.)
    >> - local writes to the same filesystem, with the same test program,
    >> never fail.
    >> - writes from another IA32 box (all these boxes are near-clones of
    >> each other as far as software is concerned) to the NFS server box
    >> never fail.
    >> - It happens if I mount the fs with -o soft (my default for all NFS
    >> mounts for robustness-in-the-presence-of-machine-failure reasons),
    >> but also if I mount with -o hard :(( besides, the timeouts happen
    >> far too fast for it to be major timeout expiry that casues the EIOs.
    >> - The failure always occurs for writes that cross the 2^21 byte
    >> boundary, but not all such writes fail. You seem to need to have
    >> done a lot of write()s before, perhaps even starting with O_TRUNC
    >> and write()ing like mad from there on up (the WRITES_PER_OPEN
    >> #define is a way to test that; I've never had a failure for a file
    >> opened with O_APPEND, even if it crossed the 2^21 byte boundary).
    >> - It happens whether _LARGEFILE_SOURCE / _FILE_OFFSET_BITS are
    >> defined or not (I'd be amazed if this affected it, actually, but
    >> it never hurts to check).
    >> - Despite the EIO, the write actually *succeeds* most of the time
    >> (perhaps not all the time; again, I'm not sure yet). In fact...
    >> - It is quite thoroughly inconsistent. If you #define REPRODUCE to 1
    >> in the test program and fill out sizes_to_reproduce[] with a set
    >> of write() sizes that have caused the error in the past, the error
    >> happens again, but not always:

    [and more; see <>;
    note that I have seen errors on writes to files of total size <2Mb --- e.g.,
    my mail overview databases --- but I can't reproduce them with a test program

    > This beast is most probably Sparc64 or 64-bit arch specific.

    That seems very likely.

    > Try to pin down the first 2.4.20-preN where it appears.
    > Then inform NFS and Sparc64 folks.

    Done. Sorry for the delay; this box is quite hard to arrange to reboot :(

    Anyway, the problem appears in 2.4.20-pre10; I suspect

    Trond Myklebust <>:
    o Workaround NFS hangs introduced in 2.4.20-pre

    (so Cc:ed)

    Does anyone have a pointer to this patch so I can try reversing it from
    2.4.20pre10? (I can't see it on l-k, but since I don't know what it
    looks like it's hard to find it in the archives; I don't have bitkeeper
    on this machine, and can't, as one of my current projects involves
    version-control filesystems).

    Anyone got any other ideas, suggestions, or anything?


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