Re: [PATCH v7 6/7] mm/madvise: employ mmget_still_valid for write lock
From: Vlastimil Babka <hidden>
Date: 2020-03-06 12:52:14
Also in:
linux-mm, lkml
On 3/2/20 8:36 PM, Minchan Kim wrote:
quoted hunk ↗ jump to hunk
From: Oleksandr Natalenko <redacted> Do the very same trick as we already do since 04f5866e41fb. KSM hints will require locking mmap_sem for write since they modify vm_flags, so for remote KSM hinting this additional check is needed. Reviewed-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Oleksandr Natalenko <redacted> Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/madvise.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/mm/madvise.c b/mm/madvise.c index e794367f681e..e77c6c1fad34 100644 --- a/mm/madvise.c +++ b/mm/madvise.c@@ -1118,6 +1118,8 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm, if (write) { if (down_write_killable(&mm->mmap_sem)) return -EINTR; + if (current->mm != mm && !mmget_still_valid(mm)) + goto skip_mm;
This will return 0, is that correct? Shoudln't there be a similar error e.g. as when finding the task by pid fails (-ESRCH ?), because IIUC the task here is going away and dumping the core?
quoted hunk ↗ jump to hunk
} else { down_read(&mm->mmap_sem); }@@ -1169,6 +1171,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm, } out: blk_finish_plug(&plug); +skip_mm: if (write) up_write(&mm->mmap_sem); else