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Subject[PATCH 4.14 160/166] s390/dasd: Fix zero write for FBA devices
Date
From: Jan Höppner <hoeppner@linux.ibm.com>

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@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Cc: <stable@vger.kernel.org> # 4.14+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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
@@ -39,6 +39,7 @@
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;
@@ -269,7 +270,7 @@ 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;
}

/*
@@ -808,6 +809,11 @@ 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();
@@ -819,6 +825,7 @@ 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);

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