lkml.org 
[lkml]   [2016]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.2.y-ckt 087/218] md/raid5: preserve STRIPE_PREREAD_ACTIVE in break_stripe_batch_list
    Date
    4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: NeilBrown <neilb@suse.com>

    commit 550da24f8d62fe81f3c13e3ec27602d6e44d43dc upstream.

    break_stripe_batch_list breaks up a batch and copies some flags from
    the batch head to the members, preserving others.

    It doesn't preserve or copy STRIPE_PREREAD_ACTIVE. This is not
    normally a problem as STRIPE_PREREAD_ACTIVE is cleared when a
    stripe_head is added to a batch, and is not set on stripe_heads
    already in a batch.

    However there is no locking to ensure one thread doesn't set the flag
    after it has just been cleared in another. This does occasionally happen.

    md/raid5 maintains a count of the number of stripe_heads with
    STRIPE_PREREAD_ACTIVE set: conf->preread_active_stripes. When
    break_stripe_batch_list clears STRIPE_PREREAD_ACTIVE inadvertently
    this could becomes incorrect and will never again return to zero.

    md/raid5 delays the handling of some stripe_heads until
    preread_active_stripes becomes zero. So when the above mention race
    happens, those stripe_heads become blocked and never progress,
    resulting is write to the array handing.

    So: change break_stripe_batch_list to preserve STRIPE_PREREAD_ACTIVE
    in the members of a batch.

    URL: https://bugzilla.kernel.org/show_bug.cgi?id=108741
    URL: https://bugzilla.redhat.com/show_bug.cgi?id=1258153
    URL: http://thread.gmane.org/5649C0E9.2030204@zoner.cz
    Reported-by: Martin Svec <martin.svec@zoner.cz> (and others)
    Tested-by: Tom Weber <linux@junkyard.4t2.com>
    Fixes: 1b956f7a8f9a ("md/raid5: be more selective about distributing flags across batch.")
    Signed-off-by: NeilBrown <neilb@suse.com>
    Signed-off-by: Shaohua Li <shli@fb.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/md/raid5.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
    index 71d7cf7..f6be7c4 100644
    --- a/drivers/md/raid5.c
    +++ b/drivers/md/raid5.c
    @@ -4236,7 +4236,6 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
    WARN_ON_ONCE(sh->state & ((1 << STRIPE_ACTIVE) |
    (1 << STRIPE_SYNCING) |
    (1 << STRIPE_REPLACED) |
    - (1 << STRIPE_PREREAD_ACTIVE) |
    (1 << STRIPE_DELAYED) |
    (1 << STRIPE_BIT_DELAY) |
    (1 << STRIPE_FULL_WRITE) |
    @@ -4251,6 +4250,7 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
    (1 << STRIPE_REPLACED)));

    set_mask_bits(&sh->state, ~(STRIPE_EXPAND_SYNC_FLAGS |
    + (1 << STRIPE_PREREAD_ACTIVE) |
    (1 << STRIPE_DEGRADED)),
    head_sh->state & (1 << STRIPE_INSYNC));

    --
    2.7.4
    \
     
     \ /
      Last update: 2016-03-31 23:21    [W:4.373 / U:0.840 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site