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Tue, 06 Oct 2026 18:43:11 -0700 (PDT) From: Pavel Begunkov To: linux-block@vger.kernel.org Cc: asml.silence@gmail.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Christoph Hellwig , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , Keith Busch , Sagi Grimberg , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Jens Axboe , Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Matthew Brost , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , dm-devel@lists.linux.dev Subject: [PATCH v9 02/13] iov_iter: add iterator type for dmabuf maps Date: Wed, 7 Oct 2026 02:42:45 +0100 Message-ID: X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce a new iterator type for dmabuf maps. The map in an opaque object with internals and format specific to the subsystem / driver, and only it can use that subsystem / driver for issuing IO. The task of the middle layers is to pass the map / iterator further down, maybe doing basic splitting and length checking. The iterator can only be used by operations of the file the associated map was created for. Suggested-by: Keith Busch Reviewed-by: Christoph Hellwig Signed-off-by: Pavel Begunkov --- include/linux/iov_iter.h | 2 ++ include/linux/uio.h | 11 +++++++++++ lib/iov_iter.c | 29 +++++++++++++++++++++++------ 3 files changed, 36 insertions(+), 6 deletions(-) diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h index f9a17fbbd398..2f91884d733b 100644 --- a/include/linux/iov_iter.h +++ b/include/linux/iov_iter.h @@ -310,6 +310,8 @@ size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_folioq(iter, len, priv, priv2, step); if (iov_iter_is_xarray(iter)) return iterate_xarray(iter, len, priv, priv2, step); + if (WARN_ON_ONCE(iov_iter_is_dmabuf_map(iter))) + return 0; return iterate_discard(iter, len, priv, priv2, step); } diff --git a/include/linux/uio.h b/include/linux/uio.h index fe2e985d74d2..638c1116e912 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -12,6 +12,7 @@ struct page; struct folio_queue; +struct dma_buf_io_map; typedef unsigned int __bitwise iov_iter_extraction_t; @@ -29,6 +30,7 @@ enum iter_type { ITER_FOLIOQ, ITER_XARRAY, ITER_DISCARD, + ITER_DMABUF_MAP, }; #define ITER_SOURCE 1 // == WRITE @@ -71,6 +73,7 @@ struct iov_iter { const struct folio_queue *folioq; struct xarray *xarray; void __user *ubuf; + struct dma_buf_io_map *dmabuf_map; }; size_t count; }; @@ -155,6 +158,11 @@ static inline bool iov_iter_is_xarray(const struct iov_iter *i) return iov_iter_type(i) == ITER_XARRAY; } +static inline bool iov_iter_is_dmabuf_map(const struct iov_iter *i) +{ + return iov_iter_type(i) == ITER_DMABUF_MAP; +} + static inline unsigned char iov_iter_rw(const struct iov_iter *i) { return i->data_source ? WRITE : READ; @@ -300,6 +308,9 @@ void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction, unsigned int first_slot, unsigned int offset, size_t count); void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray, loff_t start, size_t count); +void iov_iter_dmabuf_map(struct iov_iter *i, unsigned int direction, + struct dma_buf_io_map *map, + loff_t off, size_t count); ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, size_t *start); ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 2072c04e99d0..6831a5d9396e 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -575,7 +575,8 @@ void iov_iter_advance(struct iov_iter *i, size_t size) { if (unlikely(i->count < size)) size = i->count; - if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) { + if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i)) || + unlikely(iov_iter_is_dmabuf_map(i))) { i->iov_offset += size; i->count -= size; } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) { @@ -631,7 +632,8 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll) return; } unroll -= i->iov_offset; - if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) { + if (iov_iter_is_xarray(i) || iter_is_ubuf(i) || + iov_iter_is_dmabuf_map(i)) { BUG(); /* We should never go beyond the start of the specified * range since we might then be straying into pages that * aren't pinned. @@ -775,6 +777,20 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction, } EXPORT_SYMBOL(iov_iter_xarray); +void iov_iter_dmabuf_map(struct iov_iter *i, unsigned int direction, + struct dma_buf_io_map *map, + loff_t off, size_t count) +{ + WARN_ON(direction & ~(READ | WRITE)); + *i = (struct iov_iter){ + .iter_type = ITER_DMABUF_MAP, + .data_source = direction, + .dmabuf_map = map, + .count = count, + .iov_offset = off, + }; +} + /** * iov_iter_discard - Initialise an I/O iterator that discards data * @i: The iterator to initialise. @@ -856,7 +872,7 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) return iov_iter_alignment_bvec(i); /* With both xarray and folioq types, we're dealing with whole folios. */ - if (iov_iter_is_folioq(i)) + if (iov_iter_is_folioq(i) || iov_iter_is_dmabuf_map(i)) return i->iov_offset | i->count; if (iov_iter_is_xarray(i)) return (i->xarray_start + i->iov_offset) | i->count; @@ -872,7 +888,7 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i) size_t size = i->count; unsigned k; - if (iter_is_ubuf(i)) + if (iter_is_ubuf(i) || iov_iter_is_dmabuf_map(i)) return 0; if (WARN_ON(!iter_is_iovec(i))) @@ -1469,11 +1485,12 @@ EXPORT_SYMBOL_GPL(import_ubuf); void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state) { if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) && - !iter_is_ubuf(i)) && !iov_iter_is_kvec(i)) + !iter_is_ubuf(i) && !iov_iter_is_kvec(i) && + !iov_iter_is_dmabuf_map(i))) return; i->iov_offset = state->iov_offset; i->count = state->count; - if (iter_is_ubuf(i)) + if (iter_is_ubuf(i) || iov_iter_is_dmabuf_map(i)) return; /* * For the *vec iters, nr_segs + iov is constant - if we increment -- 2.54.0