diff options
| author | Brian Geffon <bgeffon@google.com> | 2022-10-03 10:48:32 -0400 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-10-12 18:51:50 -0700 |
| commit | 94541bc3fbde45bbd40e7989995246b22732679a (patch) | |
| tree | 2ffdc0f4f3fb09860a15bc1406ff7588c21ec394 /drivers | |
| parent | 14c2ac36811b82479b1138383b2c9ff1ab6ba47d (diff) | |
zram: always expose rw_page
Currently zram will adjust its fops to a version which does not contain
rw_page when a backing device has been assigned. This is done to prevent
upper layers from assuming a synchronous operation when a page may have
been written back. This forces every operation through bio which has
overhead associated with bio_alloc/frees.
The code can be simplified to always expose an rw_page method and only in
the rare event that a page is written back we instead will return
-EOPNOTSUPP forcing the upper layer to fallback to bio.
Link: https://lkml.kernel.org/r/20221003144832.2906610-1-bgeffon@google.com
Signed-off-by: Brian Geffon <bgeffon@google.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/block/zram/zram_drv.c | 26 |
1 files changed, 3 insertions, 23 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 43eeef2b9fbe..2ba5c98319e5 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -52,9 +52,6 @@ static unsigned int num_devices = 1; static size_t huge_class_size; static const struct block_device_operations zram_devops; -#ifdef CONFIG_ZRAM_WRITEBACK -static const struct block_device_operations zram_wb_devops; -#endif static void zram_free_page(struct zram *zram, size_t index); static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, @@ -546,17 +543,6 @@ static ssize_t backing_dev_store(struct device *dev, zram->backing_dev = backing_dev; zram->bitmap = bitmap; zram->nr_pages = nr_pages; - /* - * With writeback feature, zram does asynchronous IO so it's no longer - * synchronous device so let's remove synchronous io flag. Othewise, - * upper layer(e.g., swap) could wait IO completion rather than - * (submit and return), which will cause system sluggish. - * Furthermore, when the IO function returns(e.g., swap_readpage), - * upper layer expects IO was done so it could deallocate the page - * freely but in fact, IO is going on so finally could cause - * use-after-free when the IO is really done. - */ - zram->disk->fops = &zram_wb_devops; up_write(&zram->init_lock); pr_info("setup backing device %s\n", file_name); @@ -1270,6 +1256,9 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index, struct bio_vec bvec; zram_slot_unlock(zram, index); + /* A null bio means rw_page was used, we must fallback to bio */ + if (!bio) + return -EOPNOTSUPP; bvec.bv_page = page; bvec.bv_len = PAGE_SIZE; @@ -1856,15 +1845,6 @@ static const struct block_device_operations zram_devops = { .owner = THIS_MODULE }; -#ifdef CONFIG_ZRAM_WRITEBACK -static const struct block_device_operations zram_wb_devops = { - .open = zram_open, - .submit_bio = zram_submit_bio, - .swap_slot_free_notify = zram_slot_free_notify, - .owner = THIS_MODULE -}; -#endif - static DEVICE_ATTR_WO(compact); static DEVICE_ATTR_RW(disksize); static DEVICE_ATTR_RO(initstate); |