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| author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2019-11-21 17:54:01 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2019-12-19 15:59:03 +0000 |
| commit | 79cf668f6a1336c35e2a7e9fb39cbd325d408484 (patch) | |
| tree | 19edf93c9d04577cc0b264907c52a6297437ffe2 | |
| parent | 5d9b8c6e7ab6130e238269dbbe26de0c75724340 (diff) | |
| download | linux-stable-79cf668f6a1336c35e2a7e9fb39cbd325d408484.tar.gz linux-stable-79cf668f6a1336c35e2a7e9fb39cbd325d408484.tar.bz2 linux-stable-79cf668f6a1336c35e2a7e9fb39cbd325d408484.zip | |
mm/ksm.c: don't WARN if page is still mapped in remove_stable_node()
commit 9a63236f1ad82d71a98aa80320b6cb618fb32f44 upstream.
It's possible to hit the WARN_ON_ONCE(page_mapped(page)) in
remove_stable_node() when it races with __mmput() and squeezes in
between ksm_exit() and exit_mmap().
WARNING: CPU: 0 PID: 3295 at mm/ksm.c:888 remove_stable_node+0x10c/0x150
Call Trace:
remove_all_stable_nodes+0x12b/0x330
run_store+0x4ef/0x7b0
kernfs_fop_write+0x200/0x420
vfs_write+0x154/0x450
ksys_write+0xf9/0x1d0
do_syscall_64+0x99/0x510
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Remove the warning as there is nothing scary going on.
Link: http://lkml.kernel.org/r/20191119131850.5675-1-aryabinin@virtuozzo.com
Fixes: cbf86cfe04a6 ("ksm: remove old stable nodes more thoroughly")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | mm/ksm.c | 14 |
1 files changed, 7 insertions, 7 deletions
@@ -715,13 +715,13 @@ static int remove_stable_node(struct stable_node *stable_node) return 0; } - if (WARN_ON_ONCE(page_mapped(page))) { - /* - * This should not happen: but if it does, just refuse to let - * merge_across_nodes be switched - there is no need to panic. - */ - err = -EBUSY; - } else { + /* + * Page could be still mapped if this races with __mmput() running in + * between ksm_exit() and exit_mmap(). Just refuse to let + * merge_across_nodes/max_page_sharing be switched. + */ + err = -EBUSY; + if (!page_mapped(page)) { /* * The stable node did not yet appear stale to get_ksm_page(), * since that allows for an unmapped ksm page to be recognized |