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The pages used for > > No, it was used with zram_rw_page since rw_page didn't carry the bio. > >> this operation is never locked or have the writeback set. So, it is safe > > VM had the page lock and wait to unlock. > >> to remove the call to page_endio() function that unlocks or marks >> writeback end on the page. >> >> Rename the endio handler from zram_page_end_io to zram_read_end_io as >> the call to page_endio() is removed and to associate the callback to the >> operation it is used in. > I revisited the code again. Let me know if I got it right. When we trigger writeback, we will always call zram_bvec_read() only if ZRAM_WB is not set. That means we will only call zram_read_from_zspool() in __zram_bvec_read when parent bio set to NULL. static ssize_t writeback_store(struct device *dev, ... { if (zram_test_flag(zram, index, ZRAM_WB) || zram_test_flag(zram, index, ZRAM_SAME) || zram_test_flag(zram, index, ZRAM_UNDER_WB)) goto next; ... if (zram_bvec_read(zram, &bvec, index, 0, NULL)) { ... } static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index, struct bio *bio, bool partial_io) { .... if (!zram_test_flag(zram, index, ZRAM_WB)) { /* Slot should be locked through out the function call */ ret = zram_read_from_zspool(zram, page, index); zram_slot_unlock(zram, index); } else { /* Slot should be unlocked before the function call */ zram_slot_unlock(zram, index); ret = zram_bvec_read_from_bdev(zram, page, index, bio, partial_io); } .... } > Since zram removed the rw_page and IO comes with bio from now on, > IIUC, we are fine since every IO will go with chained-IO. Right? > We will never call zram_bvec_read_from_bdev() with parent bio set to NULL. IOW, we will always only hit the bio_chain case in read_from_bdev_async. So we could do the following?: diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index b7bb52f8dfbd..2341f4009b0f 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -606,15 +606,6 @@ static void free_block_bdev(struct zram *zram, unsigned long blk_idx) atomic64_dec(&zram->stats.bd_count); } -static void zram_page_end_io(struct bio *bio) -{ - struct page *page = bio_first_page_all(bio); - - page_endio(page, op_is_write(bio_op(bio)), - blk_status_to_errno(bio->bi_status)); - bio_put(bio); -} - /* * Returns 1 if the submission is successful. */ @@ -634,9 +625,7 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec, return -EIO; } - if (!parent) - bio->bi_end_io = zram_page_end_io; - else + if (parent) bio_chain(bio, parent); submit_bio(bio);