On Thu, May 31, 2018 at 4:36 PM, Robert Elliott <[email protected]> wrote:
> The pmem driver don't honor a forced read-only setting for very long:
> $ blockdev --setro /dev/pmem0
> $ blockdev --getro /dev/pmem0
> 1
>
> followed by various commands like these:
> $ blockdev --rereadpt /dev/pmem0
> or
> $ mkfs.ext4 /dev/pmem0
>
> results in this in the kernel serial log:
> nd_pmem namespace0.0: region0 read-write, marking pmem0 read-write
>
> with the read-only setting lost:
> $ blockdev --getro /dev/pmem0
> 0
>
> That's from bus.c nvdimm_revalidate_disk(), which always applies the
> setting from nd_region (which is initially based on the ACPI NFIT
> NVDIMM state flags not_armed bit).
>
> In contrast, commit 20bd1d026aac ("scsi: sd: Keep disk read-only when
> re-reading partition") fixed this issue for SCSI devices to preserve
> the previous setting if it was set to read-only.
>
> This patch modifies bus.c to preserve any previous read-only setting.
> It also eliminates the kernel serial log print except for cases where
> read-write is changed to read-only, so it doesn't print read-only to
> read-only non-changes.
>
> Signed-off-by: Robert Elliott <[email protected]>
Looks good to me. I'll also add the FIxes: tag and Cc: stable when applying.
One small nit below that I'll fixup when applying.
> ---
> drivers/nvdimm/bus.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
> index a64023690cad..87762afa45b0 100644
> --- a/drivers/nvdimm/bus.c
> +++ b/drivers/nvdimm/bus.c
> @@ -566,14 +566,17 @@ int nvdimm_revalidate_disk(struct gendisk *disk)
> {
> struct device *dev = disk_to_dev(disk)->parent;
> struct nd_region *nd_region = to_nd_region(dev->parent);
> - const char *pol = nd_region->ro ? "only" : "write";
> + int disk_ro = get_disk_ro(disk);
>
> - if (nd_region->ro == get_disk_ro(disk))
> + /* upgrade to read-only if the region is read-only
> + * preserve as read-only if the disk is already read-only
> + */
> + if (disk_ro || nd_region->ro == disk_ro)
> return 0;
The comment style in libnvdimm for a multi-line comment starts with /*
on a line by itself.
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