From: Huang Ying <ying.huang@xxxxxxxxx> In this patch, BIO_MAX_PAGES is changed from 256 to HPAGE_PMD_NR if CONFIG_THP_SWAP is enabled and HPAGE_PMD_NR > 256. This is to support THP (Transparent Huge Page) swap optimization. Where the THP will be write to disk as a whole instead of HPAGE_PMD_NR normal pages to batch the various operations during swap. And the page is likely to be written to disk to free memory when system memory goes really low, the memory pool need to be used to avoid deadlock. Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Ming Lei <tom.leiming@xxxxxxxxx> Cc: Shaohua Li <shli@xxxxxx> Cc: linux-block@xxxxxxxxxxxxxxx --- include/linux/bio.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/bio.h b/include/linux/bio.h index d1b04b0e99cf..314796486507 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -38,7 +38,15 @@ #define BIO_BUG_ON #endif +#ifdef CONFIG_THP_SWAP +#if HPAGE_PMD_NR > 256 +#define BIO_MAX_PAGES HPAGE_PMD_NR +#else #define BIO_MAX_PAGES 256 +#endif +#else +#define BIO_MAX_PAGES 256 +#endif #define bio_prio(bio) (bio)->bi_ioprio #define bio_set_prio(bio, prio) ((bio)->bi_ioprio = prio) -- 2.11.0
