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io_uring: allow allocated fixed files for openat/openat2
If the application passes in IORING_FILE_INDEX_ALLOC as the file_slot, then that's a hint to allocate a fixed file descriptor rather than have one be passed in directly. This can be useful for having io_uring manage the direct descriptor space. Normal open direct requests will complete with 0 for success, and < 0 in case of error. If io_uring is asked to allocated the direct descriptor, then the direct descriptor is returned in case of success. Reviewed-by: Hao Xu <howeyxu@tencent.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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b70b8e3331
commit
1339f24b33
2 changed files with 42 additions and 3 deletions
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@ -4697,7 +4697,7 @@ static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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return __io_openat_prep(req, sqe);
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}
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static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
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static int io_file_bitmap_get(struct io_ring_ctx *ctx)
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{
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struct io_file_table *table = &ctx->file_table;
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unsigned long nr = ctx->nr_user_files;
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@ -4722,6 +4722,36 @@ static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
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return -ENFILE;
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}
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static int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
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struct file *file, unsigned int file_slot)
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{
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bool alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;
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struct io_ring_ctx *ctx = req->ctx;
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int ret;
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if (alloc_slot) {
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io_ring_submit_lock(ctx, issue_flags);
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ret = io_file_bitmap_get(ctx);
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if (unlikely(ret < 0)) {
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io_ring_submit_unlock(ctx, issue_flags);
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return ret;
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}
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file_slot = ret;
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} else {
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file_slot--;
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}
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ret = io_install_fixed_file(req, file, issue_flags, file_slot);
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if (alloc_slot) {
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io_ring_submit_unlock(ctx, issue_flags);
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if (!ret)
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return file_slot;
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}
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return ret;
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}
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static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct open_flags op;
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@ -4777,8 +4807,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
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if (!fixed)
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fd_install(ret, file);
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else
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ret = io_install_fixed_file(req, file, issue_flags,
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req->open.file_slot - 1);
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ret = io_fixed_fd_install(req, issue_flags, file,
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req->open.file_slot);
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err:
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putname(req->open.filename);
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req->flags &= ~REQ_F_NEED_CLEANUP;
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@ -63,6 +63,15 @@ struct io_uring_sqe {
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__u64 __pad2[2];
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};
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/*
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* If sqe->file_index is set to this for opcodes that instantiate a new
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* direct descriptor (like openat/openat2/accept), then io_uring will allocate
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* an available direct descriptor instead of having the application pass one
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* in. The picked direct descriptor will be returned in cqe->res, or -ENFILE
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* if the space is full.
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*/
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#define IORING_FILE_INDEX_ALLOC (~0U)
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enum {
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IOSQE_FIXED_FILE_BIT,
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IOSQE_IO_DRAIN_BIT,
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