From: Minchan Kim <minchan@xxxxxxxxxx> Subject: zram: support BDI_CAP_STABLE_WRITES zram has used per-cpu stream feature from v4.7. It aims for increasing cache hit ratio of scratch buffer for compressing. Downside of that approach is that zram should ask memory space for compressed page in per-cpu context which requires stricted gfp flag which could be failed. If so, it retries to allocate memory space out of per-cpu context so it could get memory this time and compress the data again, copies it to the memory space. In this scenario, zram assumes the data should never be changed but it is not true without stable page support. So, If the data is changed under us, zram can make buffer overrun so that zsmalloc free object chain is broken so system goes crash like below https://bugzilla.suse.com/show_bug.cgi?id=997574 This patch adds BDI_CAP_STABLE_WRITES to zram for declaring "I am block device needing *stable write*". Fixes: da9556a2367c ("zram: user per-cpu compression streams") Link: http://lkml.kernel.org/r/1482366980-3782-4-git-send-email-minchan@xxxxxxxxxx Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Cc: Takashi Iwai <tiwai@xxxxxxx> Cc: Hyeoncheol Lee <cheol.lee@xxxxxxx> Cc: <yjay.kim@xxxxxxx> Cc: Sangseok Lee <sangseok.lee@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.7+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/block/zram/zram_drv.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff -puN drivers/block/zram/zram_drv.c~zram-support-bdi_cap_stable_writes drivers/block/zram/zram_drv.c --- a/drivers/block/zram/zram_drv.c~zram-support-bdi_cap_stable_writes +++ a/drivers/block/zram/zram_drv.c @@ -25,6 +25,7 @@ #include <linux/genhd.h> #include <linux/highmem.h> #include <linux/slab.h> +#include <linux/backing-dev.h> #include <linux/string.h> #include <linux/vmalloc.h> #include <linux/err.h> @@ -112,6 +113,14 @@ static inline bool is_partial_io(struct return bvec->bv_len != PAGE_SIZE; } +static void zram_revalidate_disk(struct zram *zram) +{ + revalidate_disk(zram->disk); + /* revalidate_disk reset the BDI_CAP_STABLE_WRITES so set again */ + zram->disk->queue->backing_dev_info.capabilities |= + BDI_CAP_STABLE_WRITES; +} + /* * Check if request is within bounds and aligned on zram logical blocks. */ @@ -1095,7 +1104,7 @@ static ssize_t disksize_store(struct dev zram->comp = comp; zram->disksize = disksize; set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); - revalidate_disk(zram->disk); + zram_revalidate_disk(zram); up_write(&zram->init_lock); return len; @@ -1143,7 +1152,7 @@ static ssize_t reset_store(struct device /* Make sure all the pending I/O are finished */ fsync_bdev(bdev); zram_reset_device(zram); - revalidate_disk(zram->disk); + zram_revalidate_disk(zram); bdput(bdev); mutex_lock(&bdev->bd_mutex); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
