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Subject[PATCH 1/8] pin iocb through aio.
Date
From: Linus Torvalds <torvalds@linux-foundation.org>

aio_poll() is not the only case that needs file pinned; worse, while
aio_read()/aio_write() can live without pinning iocb itself, the
proof is rather brittle and can easily break on later changes.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/aio.c | 37 +++++++++++++++++++++----------------
1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 3d9669d011b9..363d7d7c8bff 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1022,6 +1022,9 @@ static bool get_reqs_available(struct kioctx *ctx)
/* aio_get_req
* Allocate a slot for an aio request.
* Returns NULL if no requests are free.
+ *
+ * The refcount is initialized to 2 - one for the async op completion,
+ * one for the synchronous code that does this.
*/
static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
{
@@ -1034,7 +1037,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
percpu_ref_get(&ctx->reqs);
req->ki_ctx = ctx;
INIT_LIST_HEAD(&req->ki_list);
- refcount_set(&req->ki_refcnt, 0);
+ refcount_set(&req->ki_refcnt, 2);
req->ki_eventfd = NULL;
return req;
}
@@ -1067,15 +1070,18 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
return ret;
}

+static inline void iocb_destroy(struct aio_kiocb *iocb)
+{
+ if (iocb->ki_filp)
+ fput(iocb->ki_filp);
+ percpu_ref_put(&iocb->ki_ctx->reqs);
+ kmem_cache_free(kiocb_cachep, iocb);
+}
+
static inline void iocb_put(struct aio_kiocb *iocb)
{
- if (refcount_read(&iocb->ki_refcnt) == 0 ||
- refcount_dec_and_test(&iocb->ki_refcnt)) {
- if (iocb->ki_filp)
- fput(iocb->ki_filp);
- percpu_ref_put(&iocb->ki_ctx->reqs);
- kmem_cache_free(kiocb_cachep, iocb);
- }
+ if (refcount_dec_and_test(&iocb->ki_refcnt))
+ iocb_destroy(iocb);
}

static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb,
@@ -1749,9 +1755,6 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
INIT_LIST_HEAD(&req->wait.entry);
init_waitqueue_func_entry(&req->wait, aio_poll_wake);

- /* one for removal from waitqueue, one for this function */
- refcount_set(&aiocb->ki_refcnt, 2);
-
mask = vfs_poll(req->file, &apt.pt) & req->events;
if (unlikely(!req->head)) {
/* we did not manage to set up a waitqueue, done */
@@ -1782,7 +1785,6 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)

if (mask)
aio_poll_complete(aiocb, mask);
- iocb_put(aiocb);
return 0;
}

@@ -1873,18 +1875,21 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
break;
}

+ /* Done with the synchronous reference */
+ iocb_put(req);
+
/*
* If ret is 0, we'd either done aio_complete() ourselves or have
* arranged for that to be done asynchronously. Anything non-zero
* means that we need to destroy req ourselves.
*/
- if (ret)
- goto out_put_req;
- return 0;
+ if (!ret)
+ return 0;
+
out_put_req:
if (req->ki_eventfd)
eventfd_ctx_put(req->ki_eventfd);
- iocb_put(req);
+ iocb_destroy(req);
out_put_reqs_available:
put_reqs_available(ctx, 1);
return ret;
--
2.11.0
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