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Sun, 03 May 2020 05:53:19 -0700 (PDT) To: Jens Axboe , Bijan Mottahedeh Cc: io-uring References: <1588207670-65832-1-git-send-email-bijan.mottahedeh@oracle.com> <05997981-047c-a87b-c875-6ea7b229f586@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Subject: Re: [PATCH 1/1] io_uring: use proper references for fallback_req locking Message-ID: <07fda8ac-93e4-e488-0575-026b339d2c36@gmail.com> Date: Sun, 3 May 2020 15:52:13 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <05997981-047c-a87b-c875-6ea7b229f586@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 30/04/2020 17:52, Jens Axboe wrote: > On 4/29/20 6:47 PM, Bijan Mottahedeh wrote: >> Use ctx->fallback_req address for test_and_set_bit_lock() and >> clear_bit_unlock(). > > Thanks, applied. > How about getting rid of it? As once was fairly noticed, we're screwed in many other ways in case of OOM. Otherwise we at least need to make async context allocation more resilient. Signed-off-by: Pavel Begunkov diff --git a/fs/io_uring.c b/fs/io_uring.c index b699e9a8d247..62f9709565d0 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -282,9 +282,6 @@ struct io_ring_ctx { /* 0 is for ctx quiesce/reinit/free, 1 is for sqo_thread started */ struct completion *completions; - /* if all else fails... */ - struct io_kiocb *fallback_req; - #if defined(CONFIG_UNIX) struct socket *ring_sock; #endif @@ -911,10 +908,6 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) if (!ctx) return NULL; - ctx->fallback_req = kmem_cache_alloc(req_cachep, GFP_KERNEL); - if (!ctx->fallback_req) - goto err; - ctx->completions = kmalloc(2 * sizeof(struct completion), GFP_KERNEL); if (!ctx->completions) goto err; @@ -956,8 +949,6 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) INIT_LIST_HEAD(&ctx->inflight_list); return ctx; err: - if (ctx->fallback_req) - kmem_cache_free(req_cachep, ctx->fallback_req); kfree(ctx->completions); kfree(ctx->cancel_hash); kfree(ctx); @@ -1308,34 +1299,16 @@ static void io_cqring_add_event(struct io_kiocb *req, long res) __io_cqring_add_event(req, res, 0); } -static inline bool io_is_fallback_req(struct io_kiocb *req) -{ - return req == (struct io_kiocb *) - ((unsigned long) req->ctx->fallback_req & ~1UL); -} - -static struct io_kiocb *io_get_fallback_req(struct io_ring_ctx *ctx) -{ - struct io_kiocb *req; - - req = ctx->fallback_req; - if (!test_and_set_bit_lock(0, (unsigned long *) &ctx->fallback_req)) - return req; - - return NULL; -} - static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx, struct io_submit_state *state) { gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; struct io_kiocb *req; - if (!state) { - req = kmem_cache_alloc(req_cachep, gfp); - if (unlikely(!req)) - goto fallback; - } else if (!state->free_reqs) { + if (!state) + return kmem_cache_alloc(req_cachep, gfp); + + if (!state->free_reqs) { size_t sz; int ret; @@ -1349,7 +1322,7 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx, if (unlikely(ret <= 0)) { state->reqs[0] = kmem_cache_alloc(req_cachep, gfp); if (!state->reqs[0]) - goto fallback; + return NULL; ret = 1; } state->free_reqs = ret - 1; @@ -1360,8 +1333,6 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx, } return req; -fallback: - return io_get_fallback_req(ctx); } static inline void io_put_file(struct io_kiocb *req, struct file *file, @@ -1403,10 +1374,7 @@ static void __io_free_req(struct io_kiocb *req) } percpu_ref_put(&req->ctx->refs); - if (likely(!io_is_fallback_req(req))) - kmem_cache_free(req_cachep, req); - else - clear_bit_unlock(0, (unsigned long *) &req->ctx->fallback_req); + kmem_cache_free(req_cachep, req); } struct req_batch { @@ -1699,7 +1667,7 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx) static inline bool io_req_multi_free(struct req_batch *rb, struct io_kiocb *req) { - if ((req->flags & REQ_F_LINK_HEAD) || io_is_fallback_req(req)) + if (req->flags & REQ_F_LINK_HEAD) return false; if (!(req->flags & REQ_F_FIXED_FILE) || req->io) @@ -7296,7 +7264,6 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx) put_cred(ctx->creds); kfree(ctx->completions); kfree(ctx->cancel_hash); - kmem_cache_free(req_cachep, ctx->fallback_req); kfree(ctx); }