Re: [PATCH] mm,hwpoison: Return -EBUSY when migration fails

On Wed, Dec 09, 2020 at 11:25:31AM +0100, Vlastimil Babka wrote:

On 12/9/20 10:28 AM, Oscar Salvador wrote:

quoted

Currently, we return -EIO when we fail to migrate the page.

Migrations' failures are rather transient as they can happen due to
several reasons, e.g: high page refcount bump, mapping->migrate_page
failing etc.
All meaning that at that time the page could not be migrated, but
that has nothing to do with an EIO error.

Let us return -EBUSY instead, as we do in case we failed to isolate
the page.

While are it, let us remove the "ret" print as its value does not change.

Signed-off-by: Oscar Salvador <osalvador@suse.de>

Acked-by: Vlastimil Babka <redacted>

Technically this affects madvise(2) so let's cc linux-api. The manpage doesn't
document error codes of MADV_HWPOISON and MADV_SOFT_OFFLINE (besides EPERM)
though so nothing to adjust there. It's meant only for the hwpoison testing
suite anyway.

Well, not only for hwpoison testing suite.

RAS/CEC and GHES also use soft_offline_page by means of memory_failure_queue
in case a page cec count goes beyond a certain thereshold, but they do not
really check the return code.

Only madvise does.


-- 
Oscar Salvador
SUSE L3