On Mon, Aug 11, 2014 at 04:39:17PM +0800, Chao Yu wrote:
> Since we allocate a temporary buffer in zram_bvec_read to handle partial page
> operations in this commit 924bd88d703e53d30f393fac6117f8f1bc79aab6 (Staging:
> zram: allow partial page operations), our ->failed_reads value may be
> incorrect
> as we do not increase its value when failed to allocate the temporary buffer.
>
> Let's fix this issue and correct the annotation of failed_reads.
Good catch.
Just out of curiosity.
Did you catch it by code review or real workload?
>
> Signed-off-by: Chao Yu <chao2...@samsung.com>
> ---
> drivers/block/zram/zram_drv.c | 1 +
> drivers/block/zram/zram_drv.h | 2 +-
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index dfa4024..bf8ea1b 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -413,6 +413,7 @@ static int zram_bvec_read(struct zram *zram, struct
> bio_vec *bvec,
>
> if (!uncmem) {
> pr_info("Unable to allocate temp memory\n");
> + atomic64_inc(&zram->stats.failed_reads);
> ret = -ENOMEM;
> goto out_cleanup;
> }
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 5b0afde..e0f725c 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -84,7 +84,7 @@ struct zram_stats {
> atomic64_t compr_data_size; /* compressed size of pages stored */
> atomic64_t num_reads; /* failed + successful */
> atomic64_t num_writes; /* --do-- */
> - atomic64_t failed_reads; /* should NEVER! happen */
> + atomic64_t failed_reads; /* can happen when memory is too low */
> atomic64_t failed_writes; /* can happen when memory is too low */
> atomic64_t invalid_io; /* non-page-aligned I/O requests */
> atomic64_t notify_free; /* no. of swap slot free notifications */
> --
> 2.0.1.474.g72c7794
How abouting moving failed_reads/writes in zram_bvec_rw?
int zram_bvec_rw(..)
{
if (rw == READ) {
atomic64_inc(num_reads);
ret = zram_bvec_read(xxx);
} else {
atomic64_inc(&num_writes);
ret = zram_bvec_write(xxx);
}
if (unlikely(ret)) {
if (rw == READ)
atomic64_inc(failed_reads);
else
atomic64_inc(failed_writes);
}
}
>
>
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--
Kind regards,
Minchan Kim
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