On 2024-02-01 10:44, Mathieu Desnoyers wrote:
[...]
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 4e8fdcb3f1c8..b69c9e442cf4 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -560,17 +560,19 @@ static int pmem_attach_disk(struct device *dev,
dax_dev = alloc_dax(pmem, &pmem_dax_ops);
if (IS_ERR(dax_dev)) {
rc = PTR_ERR(dax_dev);
- goto out;
+ if (rc != -EOPNOTSUPP)
+ goto out;
If I compare the before / after this change, if previously
pmem_attach_disk() was called in a configuration with FS_DAX=n, it would
result in a NULL pointer dereference.
I was wrong. drivers/nvdimm/Kconfig has:
config BLK_DEV_PMEM
select DAX
and
drivers/nvdimm/Makefile has:
obj-$(CONFIG_BLK_DEV_PMEM) += nd_pmem.o
nd_pmem-y := pmem.o
which means that anything in pmem.c can assume that alloc_dax() is
implemented.
[...]
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 4b7ecd4fd431..f911e58a24dd 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -681,12 +681,14 @@ dcssblk_add_store(struct device *dev, struct
device_attribute *attr, const char
if (IS_ERR(dev_info->dax_dev)) {
rc = PTR_ERR(dev_info->dax_dev);
dev_info->dax_dev = NULL;
- goto put_dev;
+ if (rc != -EOPNOTSUPP)
+ goto put_dev;
config DCSSBLK selects FS_DAX_LIMITED and DAX.
I'm not sure what selecting DAX is trying to achieve here, because the
Kconfig option is "FS_DAX".
So depending on the real motivation behind this select, we may want to
consider failure rather than success in the -EOPNOTSUPP case.
I missed that alloc_dax() is implemented as not supported based on
CONFIG_DAX (not CONFIG_FS_DAX).
Therefore DCSSBLK Kconfig does the right thing and always selects DAX,
and thus an implemented version of alloc_dax().
This takes care of two of my open questions at least. :)
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
