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io_uring: return back safer resurrect

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commit f70865db5ff35f5ed0c7e9ef63e7cca3d4947f04 upstream.

Revert of revert of "io_uring: wait potential ->release() on resurrect",
which adds a helper for resurrect not racing completion reinit, as was
removed because of a strange bug with no clear root or link to the
patch.

Was improved, instead of rcu_synchronize(), just wait_for_completion()
because we're at 0 refs and it will happen very shortly. Specifically
use non-interruptible version to ignore all pending signals that may
have ended prior interruptible wait.

This reverts commit cb5e1b81304e089ee3ca948db4d29f71902eb575.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7a080c20f686d026efade810b116b72f88abaff9.1618101759.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2021-04-11 01:46:40 +01:00 committed by Greg Kroah-Hartman
parent 8fdaab341b
commit dc1163203a
1 changed files with 14 additions and 4 deletions
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18
fs/io_uring.c
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@ -1009,6 +1009,18 @@ static inline bool __io_match_files(struct io_kiocb *req,
req->work.identity->files == files;
}
static void io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
{
bool got = percpu_ref_tryget(ref);
/* already at zero, wait for ->release() */
if (!got)
wait_for_completion(compl);
percpu_ref_resurrect(ref);
if (got)
percpu_ref_put(ref);
}
static bool io_match_task(struct io_kiocb *head,
struct task_struct *task,
struct files_struct *files)
@ -9757,12 +9769,11 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (ret < 0)
break;
} while (1);
mutex_lock(&ctx->uring_lock);
if (ret) {
percpu_ref_resurrect(&ctx->refs);
goto out_quiesce;
io_refs_resurrect(&ctx->refs, &ctx->ref_comp);
return ret;
}
}
@ -9855,7 +9866,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (io_register_op_must_quiesce(opcode)) {
/* bring the ctx back to life */
percpu_ref_reinit(&ctx->refs);
out_quiesce:
reinit_completion(&ctx->ref_comp);
}
return ret;