This is a note to let you know that I've just added the patch titled s390/dasd: Fix zero write for FBA devices to the 5.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: s390-dasd-fix-zero-write-for-fba-devices.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 709192d531e5b0a91f20aa14abfe2fc27ddd47af Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jan=20H=C3=B6ppner?= <hoeppner@xxxxxxxxxxxxx> Date: Mon, 14 Sep 2020 13:56:47 +0200 Subject: s390/dasd: Fix zero write for FBA devices MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Jan Höppner <hoeppner@xxxxxxxxxxxxx> commit 709192d531e5b0a91f20aa14abfe2fc27ddd47af upstream. A discard request that writes zeros using the global kernel internal ZERO_PAGE will fail for machines with more than 2GB of memory due to the location of the ZERO_PAGE. Fix this by using a driver owned global zero page allocated with GFP_DMA flag set. Fixes: 28b841b3a7cb ("s390/dasd: Add discard support for FBA devices") Signed-off-by: Jan Höppner <hoeppner@xxxxxxxxxxxxx> Reviewed-by: Stefan Haberland <sth@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # 4.14+ Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/s390/block/dasd_fba.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/drivers/s390/block/dasd_fba.c +++ b/drivers/s390/block/dasd_fba.c @@ -40,6 +40,7 @@ MODULE_LICENSE("GPL"); static struct dasd_discipline dasd_fba_discipline; +static void *dasd_fba_zero_page; struct dasd_fba_private { struct dasd_fba_characteristics rdc_data; @@ -270,7 +271,7 @@ static void ccw_write_zero(struct ccw1 * ccw->cmd_code = DASD_FBA_CCW_WRITE; ccw->flags |= CCW_FLAG_SLI; ccw->count = count; - ccw->cda = (__u32) (addr_t) page_to_phys(ZERO_PAGE(0)); + ccw->cda = (__u32) (addr_t) dasd_fba_zero_page; } /* @@ -830,6 +831,11 @@ dasd_fba_init(void) int ret; ASCEBC(dasd_fba_discipline.ebcname, 4); + + dasd_fba_zero_page = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA); + if (!dasd_fba_zero_page) + return -ENOMEM; + ret = ccw_driver_register(&dasd_fba_driver); if (!ret) wait_for_device_probe(); @@ -841,6 +847,7 @@ static void __exit dasd_fba_cleanup(void) { ccw_driver_unregister(&dasd_fba_driver); + free_page((unsigned long)dasd_fba_zero_page); } module_init(dasd_fba_init); Patches currently in stable-queue which might be from hoeppner@xxxxxxxxxxxxx are queue-5.8/s390-dasd-fix-zero-write-for-fba-devices.patch