diff options
| author | Jeff Moyer <jmoyer@redhat.com> | 2014-09-02 13:17:00 -0400 |
|---|---|---|
| committer | Benjamin LaHaise <bcrl@kvack.org> | 2014-09-02 15:20:03 -0400 |
| commit | 2ff396be602f10b5eab8e73b24f20348fa2de159 (patch) | |
| tree | bdc814b8e0a170f1c852553230b32d888cf7fa5a | |
| parent | 7be141d0554921751db103b54e9f794956aa4f65 (diff) | |
| download | test-2ff396be602f10b5eab8e73b24f20348fa2de159.tar.gz | |
aio: add missing smp_rmb() in read_events_ring
We ran into a case on ppc64 running mariadb where io_getevents would
return zeroed out I/O events. After adding instrumentation, it became
clear that there was some missing synchronization between reading the
tail pointer and the events themselves. This small patch fixes the
problem in testing.
Thanks to Zach for helping to look into this, and suggesting the fix.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: stable@vger.kernel.org
| -rw-r--r-- | fs/aio.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/aio.c b/fs/aio.c index 97bc62cbe2dab..5f2e9c6c328e8 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1111,6 +1111,12 @@ static long aio_read_events_ring(struct kioctx *ctx, tail = ring->tail; kunmap_atomic(ring); + /* + * Ensure that once we've read the current tail pointer, that + * we also see the events that were stored up to the tail. + */ + smp_rmb(); + pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events); if (head == tail) |