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    Subject[PATCH 3.17 26/73] dm thin: fix missing out-of-data-space to write mode transition if blocks are released
    Date
    3.17-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Joe Thornber <ejt@redhat.com>

    commit 2c43fd26e46734430122b8d2ad3024bb532df3ef upstream.

    Discard bios and thin device deletion have the potential to release data
    blocks. If the thin-pool is in out-of-data-space mode, and blocks were
    released, transition the thin-pool back to full write mode.

    The correct time to do this is just after the thin-pool metadata commit.
    It cannot be done before the commit because the space maps will not
    allow immediate reuse of the data blocks in case there's a rollback
    following power failure.

    Signed-off-by: Joe Thornber <ejt@redhat.com>
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/md/dm-thin.c | 22 ++++++++++++++++++++--
    1 file changed, 20 insertions(+), 2 deletions(-)

    --- a/drivers/md/dm-thin.c
    +++ b/drivers/md/dm-thin.c
    @@ -990,6 +990,24 @@ static void schedule_external_copy(struc
    schedule_zero(tc, virt_block, data_dest, cell, bio);
    }

    +static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);
    +
    +static void check_for_space(struct pool *pool)
    +{
    + int r;
    + dm_block_t nr_free;
    +
    + if (get_pool_mode(pool) != PM_OUT_OF_DATA_SPACE)
    + return;
    +
    + r = dm_pool_get_free_block_count(pool->pmd, &nr_free);
    + if (r)
    + return;
    +
    + if (nr_free)
    + set_pool_mode(pool, PM_WRITE);
    +}
    +
    /*
    * A non-zero return indicates read_only or fail_io mode.
    * Many callers don't care about the return value.
    @@ -1004,6 +1022,8 @@ static int commit(struct pool *pool)
    r = dm_pool_commit_metadata(pool->pmd);
    if (r)
    metadata_operation_failed(pool, "dm_pool_commit_metadata", r);
    + else
    + check_for_space(pool);

    return r;
    }
    @@ -1022,8 +1042,6 @@ static void check_low_water_mark(struct
    }
    }

    -static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);
    -
    static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
    {
    int r;



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