[PATCH 1/2] aio: correct calculation of available events

[Benjamin LaHaise <bcrl@kvack.org>]

When the number of available events in the ring buffer is calculated,
the avail calculation is incorrect when head == tail.  This is harmless
in aio_read_events_ring(), but in free_ioctx() leads to the subsequent
WARN_ON(atomic_read(&ctx->reqs_available) > ctx->nr).  Correct this.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
---
 fs/aio.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 24ba228..dc52b0c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -337,7 +337,8 @@ static void free_ioctx(struct kioctx *ctx)
 	while (atomic_read(&ctx->reqs_available) < ctx->nr) {
 		wait_event(ctx->wait, head != ctx->shadow_tail);
 
-		avail = (head < ctx->shadow_tail ? ctx->shadow_tail : ctx->nr) - head;
+		avail = (head <= ctx->shadow_tail ?
+			 ctx->shadow_tail : ctx->nr) - head;
 
 		atomic_add(avail, &ctx->reqs_available);
 		head += avail;
@@ -884,7 +885,7 @@ static long aio_read_events_ring(struct kioctx *ctx,
 		goto out;
 
 	while (ret < nr) {
-		long avail = (head < ctx->shadow_tail
+		long avail = (head <= ctx->shadow_tail
 			      ? ctx->shadow_tail : ctx->nr) - head;
 		struct io_event *ev;
 		struct page *page;
-- 
1.7.4.1


-- 
"Thought is the essence of where you are now."

--
To unsubscribe, send a message with 'unsubscribe linux-aio' in
the body to majordomo@kvack.org.  For more info on Linux AIO,
see: http://www.kvack.org/aio/
Don't email: <a href=mailto:"aart@kvack.org">aart@kvack.org</a>