Re: [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm syscalls

[Vlastimil Babka]

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> This is the first step in making mmap_sem write holders killable. It

s/holders/waiters/?

> focuses on the trivial ones which are taking the lock early after
> entering the syscall and they are not changing state before.
>
> Therefore it is very easy to change them to use down_write_killable
> and immediately return with -EINTR. This will allow the waiter to
> pass away without blocking the mmap_sem which might be required to
> make a forward progress. E.g. the oom reaper will need the lock for
> reading to dismantle the OOM victim address space.
>
> The only tricky function in this patch is vm_mmap_pgoff which has many
> call sites via vm_mmap. To reduce the risk keep vm_mmap with the
> original non-killable semantic for now.
>
> vm_munmap callers do not bother checking the return value so open code
> it into the munmap syscall path for now for simplicity.
>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>