Dan Carpenter noted that handle_pending_slot_free() is racy with zram_reset_device(). Take write init_lock in zram_slot_free(), thus preventing any concurrent zram_slot_free(), zram_bvec_rw() or zram_reset_device(). This also allows to safely check zram->init_done in handle_pending_slot_free().
Initial intention was to minimze number of handle_pending_slot_free() call from zram_bvec_rw(), which were slowing down READ requests due to slot_free_lock spin lock. Jerome Marchand suggested to remove handle_pending_slot_free() from zram_bvec_rw(). Link: https://lkml.org/lkml/2013/9/9/172 Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com> --- drivers/staging/zram/zram_drv.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 91d94b5..7a2d4de 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -521,7 +521,8 @@ static void handle_pending_slot_free(struct zram *zram) while (zram->slot_free_rq) { free_rq = zram->slot_free_rq; zram->slot_free_rq = free_rq->next; - zram_free_page(zram, free_rq->index); + if (zram->init_done) + zram_free_page(zram, free_rq->index); kfree(free_rq); } spin_unlock(&zram->slot_free_lock); @@ -534,16 +535,13 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, if (rw == READ) { down_read(&zram->lock); - handle_pending_slot_free(zram); ret = zram_bvec_read(zram, bvec, index, offset, bio); up_read(&zram->lock); } else { down_write(&zram->lock); - handle_pending_slot_free(zram); ret = zram_bvec_write(zram, bvec, index, offset); up_write(&zram->lock); } - return ret; } @@ -750,12 +748,11 @@ error: static void zram_slot_free(struct work_struct *work) { - struct zram *zram; + struct zram *zram = container_of(work, struct zram, free_work); - zram = container_of(work, struct zram, free_work); - down_write(&zram->lock); + down_write(&zram->init_lock); handle_pending_slot_free(zram); - up_write(&zram->lock); + up_write(&zram->init_lock); } static void add_slot_free(struct zram *zram, struct zram_slot_free *free_rq) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
