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io_uring: enable lookup of links holding inflight files
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When a process exits, we cancel whatever requests it has pending that
are referencing the file table. However, if a link is holding a
reference, then we cannot find it by simply looking at the inflight
list.

Enable checking of the poll and timeout list to find the link, and
cancel it appropriately.

Cc: [email protected]
Reported-by: Josef <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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axboe committed Aug 12, 2020
1 parent a36da65 commit f254ac0
Showing 1 changed file with 87 additions and 10 deletions.
97 changes: 87 additions & 10 deletions fs/io_uring.c
Original file line number Diff line number Diff line change
Expand Up @@ -4937,6 +4937,7 @@ static bool io_poll_remove_one(struct io_kiocb *req)
io_cqring_fill_event(req, -ECANCELED);
io_commit_cqring(req->ctx);
req->flags |= REQ_F_COMP_LOCKED;
req_set_fail_links(req);
io_put_req(req);
}

Expand Down Expand Up @@ -5109,14 +5110,30 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
return HRTIMER_NORESTART;
}

static int __io_timeout_cancel(struct io_kiocb *req)
{
int ret;

list_del_init(&req->timeout.list);

ret = hrtimer_try_to_cancel(&req->io->timeout.timer);
if (ret == -1)
return -EALREADY;

req_set_fail_links(req);
req->flags |= REQ_F_COMP_LOCKED;
io_cqring_fill_event(req, -ECANCELED);
io_put_req(req);
return 0;
}

static int io_timeout_cancel(struct io_ring_ctx *ctx, __u64 user_data)
{
struct io_kiocb *req;
int ret = -ENOENT;

list_for_each_entry(req, &ctx->timeout_list, timeout.list) {
if (user_data == req->user_data) {
list_del_init(&req->timeout.list);
ret = 0;
break;
}
Expand All @@ -5125,15 +5142,7 @@ static int io_timeout_cancel(struct io_ring_ctx *ctx, __u64 user_data)
if (ret == -ENOENT)
return ret;

ret = hrtimer_try_to_cancel(&req->io->timeout.timer);
if (ret == -1)
return -EALREADY;

req_set_fail_links(req);
req->flags |= REQ_F_COMP_LOCKED;
io_cqring_fill_event(req, -ECANCELED);
io_put_req(req);
return 0;
return __io_timeout_cancel(req);
}

static int io_timeout_remove_prep(struct io_kiocb *req,
Expand Down Expand Up @@ -7935,6 +7944,71 @@ static bool io_wq_files_match(struct io_wq_work *work, void *data)
return work->files == files;
}

/*
* Returns true if 'preq' is the link parent of 'req'
*/
static bool io_match_link(struct io_kiocb *preq, struct io_kiocb *req)
{
struct io_kiocb *link;

if (!(preq->flags & REQ_F_LINK_HEAD))
return false;

list_for_each_entry(link, &preq->link_list, link_list) {
if (link == req)
return true;
}

return false;
}

/*
* We're looking to cancel 'req' because it's holding on to our files, but
* 'req' could be a link to another request. See if it is, and cancel that
* parent request if so.
*/
static bool io_poll_remove_link(struct io_ring_ctx *ctx, struct io_kiocb *req)
{
struct hlist_node *tmp;
struct io_kiocb *preq;
bool found = false;
int i;

spin_lock_irq(&ctx->completion_lock);
for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
struct hlist_head *list;

list = &ctx->cancel_hash[i];
hlist_for_each_entry_safe(preq, tmp, list, hash_node) {
found = io_match_link(preq, req);
if (found) {
io_poll_remove_one(preq);
break;
}
}
}
spin_unlock_irq(&ctx->completion_lock);
return found;
}

static bool io_timeout_remove_link(struct io_ring_ctx *ctx,
struct io_kiocb *req)
{
struct io_kiocb *preq;
bool found = false;

spin_lock_irq(&ctx->completion_lock);
list_for_each_entry(preq, &ctx->timeout_list, timeout.list) {
found = io_match_link(preq, req);
if (found) {
__io_timeout_cancel(preq);
break;
}
}
spin_unlock_irq(&ctx->completion_lock);
return found;
}

static void io_uring_cancel_files(struct io_ring_ctx *ctx,
struct files_struct *files)
{
Expand Down Expand Up @@ -7989,6 +8063,9 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
}
} else {
io_wq_cancel_work(ctx->io_wq, &cancel_req->work);
/* could be a link, check and remove if it is */
if (!io_poll_remove_link(ctx, cancel_req))
io_timeout_remove_link(ctx, cancel_req);
io_put_req(cancel_req);
}

Expand Down

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