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Fri, 21 Mar 2025 16:14:18 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.61]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7507E1955BFE; Fri, 21 Mar 2025 16:14:15 +0000 (UTC) From: David Howells To: Leon Romanovsky Cc: David Howells , Christian Brauner , Matthew Wilcox , Chuck Lever , Steve French , Ilya Dryomov , netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 1/4] iov_iter: Move ITER_DISCARD and ITER_XARRAY iteration out-of-line Date: Fri, 21 Mar 2025 16:14:01 +0000 Message-ID: <20250321161407.3333724-2-dhowells@redhat.com> In-Reply-To: <20250321161407.3333724-1-dhowells@redhat.com> References: <20250321161407.3333724-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Rspamd-Queue-Id: 3DE2F40017 X-Stat-Signature: rt5zz54p46ieo3dr646b5h7f9uxf5e86 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1742573667-354348 X-HE-Meta: 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 x0v8+RPa tq/zysf0/lfX8DY+HsQNP2HqRN+YgA8VhF9tszgc3+4vYEjeNN8sQKBissfjzfX5aRjrGTVuoy935SCDTRtJ367DdML361B3gyuN0mwVtrC5BTdTYPMnBauI3Dj0if2NoVfa8JiAlhLBRqZbmDm4PWxeJCXdjxmnaoUIz0DLDP7jrYJlhwynX9/bb1RvYJNA4hrVf8eXLcY5dBnGNDO90efSRKkPq2cuTJ1PeweKDhupYL6vCNKIqgUIILEguyv11dyNDTWB8On1Hs4WVy8BGN7uqVbZi21gMsl8Vf/0EaPWae7ac/elZp17jj9OvmRHsYpUQQeWFITHbKFly7ebeIQ7LAXL50VO/LPGLVfBWa50FA2lks9eiXYIRxdMGhilD/QHV X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Move ITER_DISCARD and ITER_XARRAY iteration out-of-line in preparation of adding other iteration types which will also be out-of-line. Signed-off-by: David Howells --- include/linux/iov_iter.h | 77 +++----------------------------------- lib/iov_iter.c | 81 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 86 insertions(+), 72 deletions(-) diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h index c4aa58032faf..0c47933df517 100644 --- a/include/linux/iov_iter.h +++ b/include/linux/iov_iter.h @@ -17,6 +17,9 @@ typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len, typedef size_t (*iov_ustep_f)(void __user *iter_base, size_t progress, size_t len, void *priv, void *priv2); +size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, + void *priv2, iov_ustep_f ustep, iov_step_f step); + /* * Handle ITER_UBUF. */ @@ -195,72 +198,6 @@ size_t iterate_folioq(struct iov_iter *iter, size_t len, void *priv, void *priv2 return progress; } -/* - * Handle ITER_XARRAY. - */ -static __always_inline -size_t iterate_xarray(struct iov_iter *iter, size_t len, void *priv, void *priv2, - iov_step_f step) -{ - struct folio *folio; - size_t progress = 0; - loff_t start = iter->xarray_start + iter->iov_offset; - pgoff_t index = start / PAGE_SIZE; - XA_STATE(xas, iter->xarray, index); - - rcu_read_lock(); - xas_for_each(&xas, folio, ULONG_MAX) { - size_t remain, consumed, offset, part, flen; - - if (xas_retry(&xas, folio)) - continue; - if (WARN_ON(xa_is_value(folio))) - break; - if (WARN_ON(folio_test_hugetlb(folio))) - break; - - offset = offset_in_folio(folio, start + progress); - flen = min(folio_size(folio) - offset, len); - - while (flen) { - void *base = kmap_local_folio(folio, offset); - - part = min_t(size_t, flen, - PAGE_SIZE - offset_in_page(offset)); - remain = step(base, progress, part, priv, priv2); - kunmap_local(base); - - consumed = part - remain; - progress += consumed; - len -= consumed; - - if (remain || len == 0) - goto out; - flen -= consumed; - offset += consumed; - } - } - -out: - rcu_read_unlock(); - iter->iov_offset += progress; - iter->count -= progress; - return progress; -} - -/* - * Handle ITER_DISCARD. - */ -static __always_inline -size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv2, - iov_step_f step) -{ - size_t progress = len; - - iter->count -= progress; - return progress; -} - /** * iterate_and_advance2 - Iterate over an iterator * @iter: The iterator to iterate over. @@ -306,9 +243,7 @@ size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_kvec(iter, len, priv, priv2, step); if (iov_iter_is_folioq(iter)) return iterate_folioq(iter, len, priv, priv2, step); - if (iov_iter_is_xarray(iter)) - return iterate_xarray(iter, len, priv, priv2, step); - return iterate_discard(iter, len, priv, priv2, step); + return __iterate_and_advance2(iter, len, priv, priv2, ustep, step); } /** @@ -370,9 +305,7 @@ size_t iterate_and_advance_kernel(struct iov_iter *iter, size_t len, void *priv, return iterate_kvec(iter, len, priv, priv2, step); if (iov_iter_is_folioq(iter)) return iterate_folioq(iter, len, priv, priv2, step); - if (iov_iter_is_xarray(iter)) - return iterate_xarray(iter, len, priv, priv2, step); - return iterate_discard(iter, len, priv, priv2, step); + return __iterate_and_advance2(iter, len, priv, priv2, NULL, step); } #endif /* _LINUX_IOV_ITER_H */ diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 65f550cb5081..33a8746e593e 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1927,3 +1927,84 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i, return -EFAULT; } EXPORT_SYMBOL_GPL(iov_iter_extract_pages); + +/* + * Handle ITER_XARRAY. + */ +static __always_inline +size_t iterate_xarray(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_step_f step) +{ + struct folio *folio; + size_t progress = 0; + loff_t start = iter->xarray_start + iter->iov_offset; + pgoff_t index = start / PAGE_SIZE; + XA_STATE(xas, iter->xarray, index); + + rcu_read_lock(); + xas_for_each(&xas, folio, ULONG_MAX) { + size_t remain, consumed, offset, part, flen; + + if (xas_retry(&xas, folio)) + continue; + if (WARN_ON(xa_is_value(folio))) + break; + if (WARN_ON(folio_test_hugetlb(folio))) + break; + + offset = offset_in_folio(folio, start + progress); + flen = min(folio_size(folio) - offset, len); + + while (flen) { + void *base = kmap_local_folio(folio, offset); + + part = min_t(size_t, flen, + PAGE_SIZE - offset_in_page(offset)); + remain = step(base, progress, part, priv, priv2); + kunmap_local(base); + + consumed = part - remain; + progress += consumed; + len -= consumed; + + if (remain || len == 0) + goto out; + flen -= consumed; + offset += consumed; + } + } + +out: + rcu_read_unlock(); + iter->iov_offset += progress; + iter->count -= progress; + return progress; +} + +/* + * Handle ITER_DISCARD. + */ +static __always_inline +size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_step_f step) +{ + size_t progress = len; + + iter->count -= progress; + return progress; +} + +/* + * Out of line iteration for iterator types that don't need such fast handling. + */ +size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, + void *priv2, iov_ustep_f ustep, iov_step_f step) +{ + if (iov_iter_is_discard(iter)) + return iterate_discard(iter, len, priv, priv2, step); + if (iov_iter_is_xarray(iter)) + return iterate_xarray(iter, len, priv, priv2, step); + WARN_ON(1); + return 0; +} +EXPORT_SYMBOL(__iterate_and_advance2); From patchwork Fri Mar 21 16:14:02 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 14025735 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3886DC36002 for ; Fri, 21 Mar 2025 16:14:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2B682280005; Fri, 21 Mar 2025 12:14:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 26966280001; Fri, 21 Mar 2025 12:14:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E15B280005; Fri, 21 Mar 2025 12:14:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id E3992280001 for ; 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Fri, 21 Mar 2025 16:14:24 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.61]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1FA2B19373C4; Fri, 21 Mar 2025 16:14:19 +0000 (UTC) From: David Howells To: Leon Romanovsky Cc: David Howells , Christian Brauner , Matthew Wilcox , Chuck Lever , Steve French , Ilya Dryomov , netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Trond Myklebust Subject: [RFC PATCH 2/4] iov_iter: Add an iterator-of-iterators Date: Fri, 21 Mar 2025 16:14:02 +0000 Message-ID: <20250321161407.3333724-3-dhowells@redhat.com> In-Reply-To: <20250321161407.3333724-1-dhowells@redhat.com> References: <20250321161407.3333724-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Queue-Id: 75266C001B X-Stat-Signature: debirgi9mqrfg38hy5swkrh7myo45xt4 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1742573669-434194 X-HE-Meta: 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 HYIitIVC Q0uBWgdTSlRuNn/mGlgQHRdps+m+kthCJt9WTMRmThE8qSe0UzM6YkZhLsfcjdosz80QBG8PyQEG6MLzyFkAePmfuaBbj1+x9g8UKuYkr4DLBpJyrrTpEiYeI1et/Cw+bFPYY9TZAm6dS13kW3krAV59SbnqNlBAwadJ5vh5CBJL4itAtYusorazeOgYBZsAJ650XE/EChwOk912A5sMZHnwPvgjWY1NVICpRPkFvcYbfqWerZuX988H1XMlLPXlK/XFozfgtJxT5HMRLEPKoUXhJxzFdowese9vo3LvlRlfhMD343fOTZLpn7JqZbKeoX+oH4ydVmPT13gdjQxYe6sLrMb2GSd3jYZwuzLoihmDa5KmOqiI0REtpBkTIg3a9ubXc0I5Vr+L/iOFjIAtuGz73x9SxHhyF2zmuGzChFhPR4Czn4dyiaLs1wg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add a new I/O iterator type, ITER_ITERLIST, that allows iteration over a series of I/O iterators, provided the iterators are all the same direction (all ITER_SOURCE or all ITER_DEST) and none of them are themselves ITER_ITERLIST (this function is recursive). To make reversion possible, I've added an 'orig_count' member into the iov_iter struct so that reversion of an ITER_ITERLIST can know when to go move backwards through the iter list. It might make more sense to make the iterator list element, say: struct itervec { struct iov_iter iter; size_t orig_count; }; rather than expanding struct iov_iter itself and have iov_iter_iterlist() set vec[i].orig_count from vec[i].iter->count. Also, for the moment, I've only permitted its use with source iterators (eg. sendmsg). To use this, you allocate an array of iterators and point the list iterator at it, e.g.: struct iov_iter iters[3]; struct msghdr msg; iov_iter_bvec(&iters[0], ITER_SOURCE, &head_bv, 1, sizeof(marker) + head->iov_len); iov_iter_xarray(&iters[1], ITER_SOURCE, xdr->pages, xdr->page_fpos, xdr->page_len); iov_iter_kvec(&iters[2], ITER_SOURCE, &tail_kv, 1, tail->iov_len); iov_iter_iterlist(&msg.msg_iter, ITER_SOURCE, iters, 3, size); This can be used by network filesystem protocols, such as sunrpc, to glue a header and a trailer on to some data to form a message and then dump the entire message onto the socket in a single go. [!] Note: I'm not entirely sure that this is a good idea: the problem is that it's reasonably common practice to copy an iterator by direct assignment - and that works for the existing iterators... but not this one. With the iterator-of-iterators, the list of iterators has to be modified if we recurse. It's probably fine just for calling sendmsg() from network filesystems, but I'm not 100% sure of that. Suggested-by: Trond Myklebust Signed-off-by: David Howells --- include/linux/uio.h | 15 +++++ lib/iov_iter.c | 158 +++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 172 insertions(+), 1 deletion(-) diff --git a/include/linux/uio.h b/include/linux/uio.h index 8ada84e85447..59a586333e1b 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -29,6 +29,7 @@ enum iter_type { ITER_FOLIOQ, ITER_XARRAY, ITER_DISCARD, + ITER_ITERLIST, }; #define ITER_SOURCE 1 // == WRITE @@ -71,6 +72,7 @@ struct iov_iter { const struct folio_queue *folioq; struct xarray *xarray; void __user *ubuf; + struct iov_iterlist *iterlist; }; size_t count; }; @@ -82,6 +84,11 @@ struct iov_iter { }; }; +struct iov_iterlist { + struct iov_iter iter; + size_t orig_count; +}; + typedef __u16 uio_meta_flags_t; struct uio_meta { @@ -149,6 +156,11 @@ 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_iterlist(const struct iov_iter *i) +{ + return iov_iter_type(i) == ITER_ITERLIST; +} + static inline unsigned char iov_iter_rw(const struct iov_iter *i) { return i->data_source ? WRITE : READ; @@ -302,6 +314,9 @@ 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_iterlist(struct iov_iter *i, unsigned int direction, + struct iov_iterlist *iterlist, unsigned long nr_segs, + 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 33a8746e593e..1d9190abfeb5 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -578,6 +578,19 @@ void iov_iter_advance(struct iov_iter *i, size_t size) iov_iter_folioq_advance(i, size); } else if (iov_iter_is_discard(i)) { i->count -= size; + } else if (iov_iter_is_iterlist(i)) { + i->count -= size; + for (;;) { + size_t part = umin(size, i->iterlist->iter.count); + + if (part > 0) + iov_iter_advance(&i->iterlist->iter, part); + size -= part; + if (!size) + break; + i->iterlist++; + i->nr_segs--; + } } } EXPORT_SYMBOL(iov_iter_advance); @@ -608,6 +621,23 @@ static void iov_iter_folioq_revert(struct iov_iter *i, size_t unroll) i->folioq = folioq; } +static void iov_iter_revert_iterlist(struct iov_iter *i, size_t unroll) +{ + for (;;) { + struct iov_iterlist *il = i->iterlist; + + size_t part = umin(unroll, il->orig_count - il->iter.count); + + if (part > 0) + iov_iter_revert(&il->iter, part); + unroll -= part; + if (!unroll) + break; + i->iterlist--; + i->nr_segs++; + } +} + void iov_iter_revert(struct iov_iter *i, size_t unroll) { if (!unroll) @@ -617,6 +647,8 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll) i->count += unroll; if (unlikely(iov_iter_is_discard(i))) return; + if (unlikely(iov_iter_is_iterlist(i))) + return iov_iter_revert_iterlist(i, unroll); if (unroll <= i->iov_offset) { i->iov_offset -= unroll; return; @@ -663,6 +695,8 @@ EXPORT_SYMBOL(iov_iter_revert); */ size_t iov_iter_single_seg_count(const struct iov_iter *i) { + if (iov_iter_is_iterlist(i)) + i = &i->iterlist->iter; if (i->nr_segs > 1) { if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) return min(i->count, iter_iov(i)->iov_len - i->iov_offset); @@ -787,6 +821,41 @@ void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count) } EXPORT_SYMBOL(iov_iter_discard); +/** + * iov_iter_iterlist - Initialise an I/O iterator that is a list of iterators + * @iter: The iterator to initialise. + * @direction: The direction of the transfer. + * @iterlist: The list of iterators + * @nr_segs: The number of elements in the list + * @count: The size of the I/O buffer in bytes. + * + * Set up an I/O iterator that walks over an array of other iterators. It's + * only available as a source iterator (for WRITE) and none of the iterators in + * the array can be of ITER_ITERLIST type to prevent infinite recursion. + */ +void iov_iter_iterlist(struct iov_iter *iter, unsigned int direction, + struct iov_iterlist *iterlist, unsigned long nr_segs, + size_t count) +{ + unsigned long i; + + BUG_ON(direction != WRITE); + for (i = 0; i < nr_segs; i++) { + BUG_ON(iterlist[i].iter.iter_type == ITER_ITERLIST); + BUG_ON(iterlist[i].iter.data_source != direction); + iterlist[i].orig_count = iterlist[i].iter.count; + } + + *iter = (struct iov_iter){ + .iter_type = ITER_ITERLIST, + .data_source = true, + .count = count, + .iterlist = iterlist, + .nr_segs = nr_segs, + }; +} +EXPORT_SYMBOL(iov_iter_iterlist); + static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask) { @@ -947,6 +1016,15 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) if (iov_iter_is_xarray(i)) return (i->xarray_start + i->iov_offset) | i->count; + if (iov_iter_is_iterlist(i)) { + unsigned long align = 0; + unsigned int j; + + for (j = 0; j < i->nr_segs; j++) + align |= iov_iter_alignment(&i->iterlist[j].iter); + return align; + } + return 0; } EXPORT_SYMBOL(iov_iter_alignment); @@ -1206,6 +1284,18 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, return iter_folioq_get_pages(i, pages, maxsize, maxpages, start); if (iov_iter_is_xarray(i)) return iter_xarray_get_pages(i, pages, maxsize, maxpages, start); + if (iov_iter_is_iterlist(i)) { + ssize_t size; + + while (!i->iterlist->iter.count) { + i->iterlist++; + i->nr_segs--; + } + size = __iov_iter_get_pages_alloc(&i->iterlist->iter, + pages, maxsize, maxpages, start); + i->count -= size; + return size; + } return -EFAULT; } @@ -1274,6 +1364,21 @@ static int bvec_npages(const struct iov_iter *i, int maxpages) return npages; } +static int iterlist_npages(const struct iov_iter *i, int maxpages) +{ + const struct iov_iterlist *p; + ssize_t size = i->count; + int npages = 0; + + for (p = i->iterlist; size; p++) { + size -= p->iter.count; + npages += iov_iter_npages(&p->iter, maxpages - npages); + if (unlikely(npages >= maxpages)) + return maxpages; + } + return npages; +} + int iov_iter_npages(const struct iov_iter *i, int maxpages) { if (unlikely(!i->count)) @@ -1298,6 +1403,8 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE); return min(npages, maxpages); } + if (iov_iter_is_iterlist(i)) + return iterlist_npages(i, maxpages); return 0; } EXPORT_SYMBOL(iov_iter_npages); @@ -1309,11 +1416,14 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags) return new->bvec = kmemdup(new->bvec, new->nr_segs * sizeof(struct bio_vec), flags); - else if (iov_iter_is_kvec(new) || iter_is_iovec(new)) + if (iov_iter_is_kvec(new) || iter_is_iovec(new)) /* iovec and kvec have identical layout */ return new->__iov = kmemdup(new->__iov, new->nr_segs * sizeof(struct iovec), flags); + if (WARN_ON_ONCE(iov_iter_is_iterlist(old))) + /* Don't allow dup'ing of iterlist as the cleanup is complicated */ + return NULL; return NULL; } EXPORT_SYMBOL(dup_iter); @@ -1924,6 +2034,23 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i, return iov_iter_extract_xarray_pages(i, pages, maxsize, maxpages, extraction_flags, offset0); + if (iov_iter_is_iterlist(i)) { + ssize_t size; + + while (i->nr_segs && !i->iterlist->iter.count) { + i->iterlist++; + i->nr_segs--; + } + if (!i->nr_segs) { + WARN_ON_ONCE(i->count); + return 0; + } + size = iov_iter_extract_pages(&i->iterlist->iter, + pages, maxsize, maxpages, + extraction_flags, offset0); + i->count -= size; + return size; + } return -EFAULT; } EXPORT_SYMBOL_GPL(iov_iter_extract_pages); @@ -1994,6 +2121,33 @@ size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv return progress; } +/* + * Handle iteration over ITER_ITERLIST. + */ +static size_t iterate_iterlist(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_ustep_f ustep, iov_step_f step) +{ + struct iov_iterlist *p = iter->iterlist; + size_t progress = 0; + + do { + size_t consumed; + + consumed = iterate_and_advance2(&p->iter, len, priv, priv2, ustep, step); + + len -= consumed; + progress += consumed; + if (p->iter.count) + break; + p++; + } while (len); + + iter->nr_segs -= p - iter->iterlist; + iter->iterlist = p; + iter->count -= progress; + return progress; +} + /* * Out of line iteration for iterator types that don't need such fast handling. */ @@ -2004,6 +2158,8 @@ size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_discard(iter, len, priv, priv2, step); if (iov_iter_is_xarray(iter)) return iterate_xarray(iter, len, priv, priv2, step); + if (iov_iter_is_iterlist(iter)) + return iterate_iterlist(iter, len, priv, priv2, ustep, step); WARN_ON(1); return 0; } From patchwork Fri Mar 21 16:14:03 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 14025736 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82451C36000 for ; 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Fri, 21 Mar 2025 12:14:31 -0400 X-MC-Unique: J_hiXevqOZKYdauQ2n8oLw-1 X-Mimecast-MFC-AGG-ID: J_hiXevqOZKYdauQ2n8oLw_1742573670 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C2B541903081; Fri, 21 Mar 2025 16:14:29 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.61]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 075461955BFE; Fri, 21 Mar 2025 16:14:25 +0000 (UTC) From: David Howells To: Leon Romanovsky Cc: David Howells , Christian Brauner , Matthew Wilcox , Chuck Lever , Steve French , Ilya Dryomov , netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 3/4] iov_iter: Add a scatterlist iterator type Date: Fri, 21 Mar 2025 16:14:03 +0000 Message-ID: <20250321161407.3333724-4-dhowells@redhat.com> In-Reply-To: <20250321161407.3333724-1-dhowells@redhat.com> References: <20250321161407.3333724-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Rspamd-Queue-Id: A4ACF100017 X-Stat-Signature: 5z7kf4xbjitdsdcfutkg5xffx4ri59i4 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1742573675-391205 X-HE-Meta: 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 woVGfZxZ iN12bTFfVyYQw+cA6W0C90CsnLSBnaMpTZy4pe3Yu3l2oR5i6g1D+crs6+LULbsomvYwN/duB3ZOatrblDSOgJSP8W0tJ1dSccalwXqeIE5i/gLmSCZ96yJj+MadpTOH6mpwOh/F256FXuJgINFFbzMhXwBpSS2n4WO5e94UuxP+OJfK4yOqvS+Khb86YNViUXJbyBnYjwMJSFosDTLYIBxSN8XTDWVsh09ymKj8R7uWQWitzn/Z4I04i6W8YnoiOpT/vv2Jyz9eqmZ/KKG2Ixdv2XnD2kygZqH2okJcuifQ86NzdK3sqvIZViCtAe49Pz95cIkHmBGz+7lBBlTugNjB99lZg9xd0OWh0ritNVkANyKDRui73b7/C2cXCqE2dPwJ0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add an iterator type that can iterate over a scatterlist. This can be used as a bridge to help convert things that take scatterlists into things that take I/O iterators. Signed-off-by: David Howells --- include/linux/uio.h | 12 ++ lib/iov_iter.c | 315 +++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 321 insertions(+), 6 deletions(-) diff --git a/include/linux/uio.h b/include/linux/uio.h index 59a586333e1b..0e50f4af6877 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -12,6 +12,7 @@ struct page; struct folio_queue; +struct scatterlist; typedef unsigned int __bitwise iov_iter_extraction_t; @@ -30,6 +31,7 @@ enum iter_type { ITER_XARRAY, ITER_DISCARD, ITER_ITERLIST, + ITER_SCATTERLIST, }; #define ITER_SOURCE 1 // == WRITE @@ -46,6 +48,7 @@ struct iov_iter { bool nofault; bool data_source; size_t iov_offset; + size_t orig_count; /* * Hack alert: overlay ubuf_iovec with iovec + count, so * that the members resolve correctly regardless of the type @@ -73,11 +76,13 @@ struct iov_iter { struct xarray *xarray; void __user *ubuf; struct iov_iterlist *iterlist; + struct scatterlist *sglist; }; size_t count; }; }; union { + struct scatterlist *sglist_head; unsigned long nr_segs; u8 folioq_slot; loff_t xarray_start; @@ -161,6 +166,11 @@ static inline bool iov_iter_is_iterlist(const struct iov_iter *i) return iov_iter_type(i) == ITER_ITERLIST; } +static inline bool iov_iter_is_scatterlist(const struct iov_iter *i) +{ + return iov_iter_type(i) == ITER_SCATTERLIST; +} + static inline unsigned char iov_iter_rw(const struct iov_iter *i) { return i->data_source ? WRITE : READ; @@ -317,6 +327,8 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray * void iov_iter_iterlist(struct iov_iter *i, unsigned int direction, struct iov_iterlist *iterlist, unsigned long nr_segs, size_t count); +void iov_iter_scatterlist(struct iov_iter *i, unsigned int direction, + struct scatterlist *sglist, 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 1d9190abfeb5..ed9859af3c5d 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -562,6 +562,26 @@ static void iov_iter_folioq_advance(struct iov_iter *i, size_t size) i->folioq = folioq; } +static void iov_iter_scatterlist_advance(struct iov_iter *i, size_t size) +{ + struct scatterlist *sg; + + if (!i->count) + return; + i->count -= size; + + size += i->iov_offset; + + for (sg = i->sglist; sg; sg_next(sg)) { + if (likely(size < sg->length)) + break; + size -= sg->length; + } + WARN_ON(!sg && size > 0); + i->iov_offset = size; + i->sglist = sg; +} + void iov_iter_advance(struct iov_iter *i, size_t size) { if (unlikely(i->count < size)) @@ -591,6 +611,8 @@ void iov_iter_advance(struct iov_iter *i, size_t size) i->iterlist++; i->nr_segs--; } + } else if (iov_iter_is_scatterlist(i)) { + iov_iter_scatterlist_advance(i, size); } } EXPORT_SYMBOL(iov_iter_advance); @@ -638,6 +660,15 @@ static void iov_iter_revert_iterlist(struct iov_iter *i, size_t unroll) } } +static void iov_iter_revert_scatterlist(struct iov_iter *i) +{ + size_t skip = i->orig_count - i->count; + + i->sglist = i->sglist_head; + i->count = i->orig_count; + iov_iter_advance(i, skip); +} + void iov_iter_revert(struct iov_iter *i, size_t unroll) { if (!unroll) @@ -649,6 +680,8 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll) return; if (unlikely(iov_iter_is_iterlist(i))) return iov_iter_revert_iterlist(i, unroll); + if (unlikely(iov_iter_is_scatterlist(i))) + return iov_iter_revert_scatterlist(i); if (unroll <= i->iov_offset) { i->iov_offset -= unroll; return; @@ -706,6 +739,8 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i) if (unlikely(iov_iter_is_folioq(i))) return !i->count ? 0 : umin(folioq_folio_size(i->folioq, i->folioq_slot), i->count); + if (unlikely(iov_iter_is_scatterlist(i))) + return !i->sglist ? 0 : umin(i->count, i->sglist->length - i->iov_offset); return i->count; } EXPORT_SYMBOL(iov_iter_single_seg_count); @@ -856,6 +891,33 @@ void iov_iter_iterlist(struct iov_iter *iter, unsigned int direction, } EXPORT_SYMBOL(iov_iter_iterlist); +/** + * iov_iter_scatterlist - Initialise an I/O iterator for a scatterlist chain + * @iter: The iterator to initialise. + * @direction: The direction of the transfer. + * @sglist: The head of the scatterlist + * @count: The size of the I/O buffer in bytes. + * + * Set up an I/O iterator that walks over a scatterlist. Because scatterlists + * can be chained and have no back pointers, reversion requires starting again + * at the beginning and counting forwards. + */ +void iov_iter_scatterlist(struct iov_iter *iter, unsigned int direction, + struct scatterlist *sglist, size_t count) +{ + WARN_ON(direction & ~(READ | WRITE)); + *iter = (struct iov_iter){ + .iter_type = ITER_SCATTERLIST, + .data_source = direction, + .sglist = sglist, + .sglist_head = sglist, + .iov_offset = 0, + .count = count, + .orig_count = count, + }; +} +EXPORT_SYMBOL(iov_iter_scatterlist); + static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask) { @@ -994,6 +1056,26 @@ static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i) return res; } +static unsigned long iov_iter_alignment_scatterlist(const struct iov_iter *i) +{ + struct scatterlist *sg; + unsigned skip = i->iov_offset; + unsigned res = 0; + size_t size = i->count; + + for (sg = i->sglist; sg; sg = sg_next(sg)) { + size_t len = sg->length - skip; + res |= (unsigned long)sg->offset + skip; + if (len > size) + len = size; + res |= len; + size -= len; + skip = 0; + } while (size); + + return res; +} + unsigned long iov_iter_alignment(const struct iov_iter *i) { if (likely(iter_is_ubuf(i))) { @@ -1024,6 +1106,8 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) align |= iov_iter_alignment(&i->iterlist[j].iter); return align; } + if (iov_iter_is_scatterlist(i)) + return iov_iter_alignment_scatterlist(i); return 0; } @@ -1058,13 +1142,8 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i) } EXPORT_SYMBOL(iov_iter_gap_alignment); -static int want_pages_array(struct page ***res, size_t size, - size_t start, unsigned int maxpages) +static int __want_pages_array(struct page ***res, unsigned int count) { - unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE); - - if (count > maxpages) - count = maxpages; WARN_ON(!count); // caller should've prevented that if (!*res) { *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL); @@ -1074,6 +1153,16 @@ static int want_pages_array(struct page ***res, size_t size, return count; } +static int want_pages_array(struct page ***res, size_t size, + size_t start, unsigned int maxpages) +{ + size_t count = DIV_ROUND_UP(size + start, PAGE_SIZE); + + if (count > maxpages) + count = maxpages; + return __want_pages_array(res, count); +} + static ssize_t iter_folioq_get_pages(struct iov_iter *iter, struct page ***ppages, size_t maxsize, unsigned maxpages, size_t *_start_offset) @@ -1186,6 +1275,52 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, return maxsize; } +static struct page *first_scatterlist_segment(const struct iov_iter *i, + size_t *size, size_t *start) +{ + struct scatterlist *sg = i->sglist; + struct page *page; + size_t skip = i->iov_offset, len; + + if (!sg) + return NULL; + + len = sg->length - skip; + if (*size > len) + *size = len; + skip += sg->offset; + page = sg_page(sg) + skip / PAGE_SIZE; + *start = skip % PAGE_SIZE; + return page; +} + +static ssize_t iter_scatterlist_get_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned maxpages, size_t *start) +{ + struct page **p, *page; + unsigned int n; + + page = first_scatterlist_segment(i, &maxsize, start); + if (!page) + return -EFAULT; + n = want_pages_array(pages, maxsize, *start, maxpages); + if (!n) + return -ENOMEM; + p = *pages; + for (int k = 0; k < n; k++) + get_page(p[k] = page + k); + maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start); + i->count -= maxsize; + i->iov_offset += maxsize; + if (i->iov_offset == i->bvec->bv_len) { + i->iov_offset = 0; + i->bvec++; + i->nr_segs--; + } + return maxsize; +} + /* must be done on non-empty ITER_UBUF or ITER_IOVEC one */ static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size) { @@ -1296,6 +1431,8 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, i->count -= size; return size; } + if (iov_iter_is_scatterlist(i)) + return iter_scatterlist_get_pages(i, pages, maxsize, maxpages, start); return -EFAULT; } @@ -1379,6 +1516,25 @@ static int iterlist_npages(const struct iov_iter *i, int maxpages) return npages; } +static int scatterlist_npages(const struct iov_iter *i, int maxpages) +{ + struct scatterlist *sg; + size_t skip = i->iov_offset, size = i->count; + int npages = 0; + + for (sg = i->sglist; sg && size; sg = sg_next(sg)) { + unsigned offs = (sg->offset + skip) % PAGE_SIZE; + size_t len = umin(sg->length - skip, size); + + size -= len; + npages += DIV_ROUND_UP(offs + len, PAGE_SIZE); + if (unlikely(npages > maxpages)) + return maxpages; + skip = 0; + } + return npages; +} + int iov_iter_npages(const struct iov_iter *i, int maxpages) { if (unlikely(!i->count)) @@ -1405,6 +1561,8 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) } if (iov_iter_is_iterlist(i)) return iterlist_npages(i, maxpages); + if (iov_iter_is_scatterlist(i)) + return scatterlist_npages(i, maxpages); return 0; } EXPORT_SYMBOL(iov_iter_npages); @@ -1792,6 +1950,107 @@ static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i, return maxsize; } +/* + * Count the number of virtually contiguous pages in a scatterlist iterator + * from the current point. + */ +static size_t count_scatterlist_contig_pages(const struct iov_iter *i, + size_t maxpages, size_t maxsize) +{ + struct scatterlist *sg; + size_t npages = 0; + size_t skip = i->iov_offset, size = umin(i->count, maxsize); + + for (sg = i->sglist; sg && size; sg = sg_next(sg)) { + size_t offs = (sg->offset + skip) % PAGE_SIZE; + size_t part = umin(sg->length - skip, size); + + if (!part) + break; + size -= part; + npages += DIV_ROUND_UP(offs + part, PAGE_SIZE); + if (unlikely(npages > maxpages)) + return maxpages; + if (((offs + part) % PAGE_SIZE) != 0) + break; + skip = 0; + } + return npages; +} + +/* + * Extract a list of contiguous pages from an ITER_FOLIOQ iterator. This does + * not get references on the pages, nor does it get a pin on them. + */ +static ssize_t iov_iter_extract_scatterlist_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned int maxpages, + iov_iter_extraction_t extraction_flags, + size_t *offset0) +{ + struct scatterlist *sg = i->sglist; + struct page **p; + size_t npages, skip, size = 0; + int nr = 0; + + if (!sg) + return 0; + + while (skip = i->iov_offset, + skip == sg->length) { + sg = sg_next(sg); + i->sglist = sg; + i->iov_offset = 0; + if (!sg) + return 0; + } + + npages = count_scatterlist_contig_pages(i, maxpages, maxsize); + + maxpages = __want_pages_array(pages, npages); + if (!maxpages) + return -ENOMEM; + *offset0 = (sg->offset + skip) & ~PAGE_MASK; + p = *pages; + + for (sg = i->sglist; sg; sg = sg_next(sg)) { + struct page *page = sg_page(sg); + size_t part = umin(sg->length - skip, maxsize); + size_t off = sg->offset + skip; + + if (!part) + break; + + page += off / PAGE_SIZE; + off %= PAGE_SIZE; + + do { + size_t chunk = umin(part, PAGE_SIZE - off); + + p[nr++] = page; + page++; + maxpages--; + maxsize -= chunk; + size += chunk; + skip += chunk; + part -= chunk; + off = 0; + } while (part && maxsize && maxpages); + + if (((sg->offset + skip + part) % PAGE_SIZE) != 0) + break; + if (!maxsize || !maxpages) { + if (!part) + sg = sg_next(sg); + break; + } + skip = 0; + } + + iov_iter_advance(i, size); + return size; +} + /* * Extract a list of virtually contiguous pages from an ITER_BVEC iterator. * This does not get references on the pages, nor does it get a pin on them. @@ -2051,6 +2310,10 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i, i->count -= size; return size; } + if (iov_iter_is_scatterlist(i)) + return iov_iter_extract_scatterlist_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); return -EFAULT; } EXPORT_SYMBOL_GPL(iov_iter_extract_pages); @@ -2148,6 +2411,44 @@ static size_t iterate_iterlist(struct iov_iter *iter, size_t len, void *priv, vo return progress; } +/* + * Handle iteration over ITER_SCATTERLIST. + */ +static size_t iterate_scatterlist(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_step_f step) +{ + struct scatterlist *sg = iter->sglist; + size_t progress = 0, skip = iter->iov_offset; + + do { + struct page *page = sg_page(sg); + size_t remain, consumed; + size_t offset = sg->offset + skip, part; + void *kaddr = kmap_local_page(page + offset / PAGE_SIZE); + + part = min3(len, + (size_t)(sg->length - skip), + (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); + remain = step(kaddr + offset % PAGE_SIZE, progress, part, priv, priv2); + kunmap_local(kaddr); + consumed = part - remain; + len -= consumed; + progress += consumed; + skip += consumed; + if (skip >= sg->length) { + skip = 0; + sg = sg_next(sg); + } + if (remain) + break; + } while (len); + + iter->sglist = sg; + iter->iov_offset = skip; + iter->count -= progress; + return progress; +} + /* * Out of line iteration for iterator types that don't need such fast handling. */ @@ -2160,6 +2461,8 @@ size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_xarray(iter, len, priv, priv2, step); if (iov_iter_is_iterlist(iter)) return iterate_iterlist(iter, len, priv, priv2, ustep, step); + if (iov_iter_is_scatterlist(iter)) + return iterate_scatterlist(iter, len, priv, priv2, step); WARN_ON(1); return 0; } From patchwork Fri Mar 21 16:14:04 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 14025737 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E2FFC36000 for ; Fri, 21 Mar 2025 16:14:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 12577280008; Fri, 21 Mar 2025 12:14:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0D57F280001; Fri, 21 Mar 2025 12:14:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E9345280008; 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Fri, 21 Mar 2025 16:14:34 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.61]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id ED872180174E; Fri, 21 Mar 2025 16:14:30 +0000 (UTC) From: David Howells To: Leon Romanovsky Cc: David Howells , Christian Brauner , Matthew Wilcox , Chuck Lever , Steve French , Ilya Dryomov , netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 4/4] iov_iter: Add a scatterlist iterator type [INCOMPLETE] Date: Fri, 21 Mar 2025 16:14:04 +0000 Message-ID: <20250321161407.3333724-5-dhowells@redhat.com> In-Reply-To: <20250321161407.3333724-1-dhowells@redhat.com> References: <20250321161407.3333724-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4E38C20017 X-Stat-Signature: 5gb48h7xb3zotesw73qtmk3fpep66bni X-HE-Tag: 1742573682-149159 X-HE-Meta: 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 a1CDB5gk VyPxxKqGWu5hOubb5s8dX/GNdWD0ZvD5w/+v/0x/GYnM6r/vxf4fMUCAwfXny6m9Lf+x8LEIqgTVMURixBpbzBA0dRUtOvUzLTf1DWQ819s/zdh5ZcsPBNS+U7cCrwdzNi8l25XeWD2SrGobSo7Iz+Uq+1ymj2WZUrOHtZJZ5TucR/mCog3McMI1sGwnW4FR6TTJQey3RXg4NEI0oAP861KwygNgSvRaImfSBNKKgi7ImNp+z0cxXUEmbxvAH5ycFPHbviEKCxjRCjw7YD36p9XLMaJWVSbGCkOGmQg+9iXBKhygLXh2Fvs33ePYLuxLAtDYmDgxVa6DOo3tCvPexf+LwlKbvzbBV0IGmXHF30kc2rMz3DijLOWjUqv9Tk0DUBPxN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add an iterator type that can iterate over a socket buffer. [!] Note this is not yet completely implemented and won't compile. Signed-off-by: David Howells --- include/linux/uio.h | 10 ++++ lib/iov_iter.c | 121 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 131 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index 0e50f4af6877..87d6ba660489 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -13,6 +13,7 @@ struct page; struct folio_queue; struct scatterlist; +struct sk_buff; typedef unsigned int __bitwise iov_iter_extraction_t; @@ -32,6 +33,7 @@ enum iter_type { ITER_DISCARD, ITER_ITERLIST, ITER_SCATTERLIST, + ITER_SKBUFF, }; #define ITER_SOURCE 1 // == WRITE @@ -77,6 +79,7 @@ struct iov_iter { void __user *ubuf; struct iov_iterlist *iterlist; struct scatterlist *sglist; + const struct sk_buff *skb; }; size_t count; }; @@ -171,6 +174,11 @@ static inline bool iov_iter_is_scatterlist(const struct iov_iter *i) return iov_iter_type(i) == ITER_SCATTERLIST; } +static inline bool iov_iter_is_skbuff(const struct iov_iter *i) +{ + return iov_iter_type(i) == ITER_SKBUFF; +} + static inline unsigned char iov_iter_rw(const struct iov_iter *i) { return i->data_source ? WRITE : READ; @@ -329,6 +337,8 @@ void iov_iter_iterlist(struct iov_iter *i, unsigned int direction, size_t count); void iov_iter_scatterlist(struct iov_iter *i, unsigned int direction, struct scatterlist *sglist, size_t count); +void iov_iter_skbuff(struct iov_iter *i, unsigned int direction, + const struct sk_buff *skb, 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 ed9859af3c5d..01215316d272 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -12,6 +12,7 @@ #include #include #include +#include static __always_inline size_t copy_to_user_iter(void __user *iter_to, size_t progress, @@ -918,6 +919,29 @@ void iov_iter_scatterlist(struct iov_iter *iter, unsigned int direction, } EXPORT_SYMBOL(iov_iter_scatterlist); +/** + * iov_iter_skbuff - Initialise an I/O iterator for a socket buffer + * @iter: The iterator to initialise. + * @direction: The direction of the transfer. + * @skb: The socket buffer + * @count: The size of the I/O buffer in bytes. + * + * Set up an I/O iterator that walks over a socket buffer. + */ +void iov_iter_skbuff(struct iov_iter *i, unsigned int direction, + const struct sk_buff *skb, size_t count) +{ + WARN_ON(direction & ~(READ | WRITE)); + *iter = (struct iov_iter){ + .iter_type = ITER_SKBUFF, + .data_source = direction, + .skb = skb, + .iov_offset = 0, + .count = count, + }; +} +EXPORT_SYMBOL(iov_iter_skbuff); + static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask) { @@ -2314,6 +2338,10 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i, return iov_iter_extract_scatterlist_pages(i, pages, maxsize, maxpages, extraction_flags, offset0); + if (iov_iter_is_skbuff(i)) + return iov_iter_extract_skbuff_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); return -EFAULT; } EXPORT_SYMBOL_GPL(iov_iter_extract_pages); @@ -2449,6 +2477,97 @@ static size_t iterate_scatterlist(struct iov_iter *iter, size_t len, void *priv, return progress; } +struct skbuff_iter_ctx { + iov_step_f step; + size_t progress; + void *priv; + void *priv2; +}; + +static bool iterate_skbuff_frag(const struct sk_buff *skb, struct skbuff_iter_ctx *ctx, + int offset, int len, int recursion_level) +{ + struct sk_buff *frag_iter; + size_t skip = offset, part, remain, consumed; + + if (unlikely(recursion_level >= 24)) + return false; + + part = skb_headlen(skb); + if (skip < part) { + part = umin(part - skip, len); + remain = ctx->step(skb->data + skip, ctx->progress, part, + ctx->priv, ctx->priv2); + consumed = part - remain; + ctx->progress += consumed; + len -= consumed; + if (remain > 0 || len <= 0) + return false; + skip = 0; + } else { + skip -= part; + } + + for (int i = 0; i < skb_shinfo(skb)->nr_frags; i++) { + const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; + size_t fsize = skb_frag_size(frag); + + if (skip >= fsize) { + skip -= fsize; + continue; + } + + part = umin(fsize - skip, len); + remain = ctx->step(skb_frag_address(frag) + skip, + ctx->progress, part, ctx->priv, ctx->priv2); + consumed = part - remain; + ctx->progress += consumed; + len -= consumed; + if (remain > 0 || len <= 0) + return false; + skip = 0; + } + + skb_walk_frags(skb, frag_iter) { + size_t fsize = frag_iter->len; + + if (skip >= fsize) { + skip -= fsize; + continue; + } + + part = umin(fsize - skip, len); + if (!iterate_skbuff_frag(frag_iter, ctx, skb_headlen(skb) + skip, + part, recursion_level + 1)) + return false; + len -= part; + if (len <= 0) + return false; + skip = 0; + } + return true; +} + +/* + * Handle iteration over ITER_SKBUFF. Modelled on __skb_to_sgvec(). + */ +static size_t iterate_skbuff(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_step_f step) +{ + struct skbuff_iter_ctx ctx = { + .step = step, + .progress = 0, + .priv = priv, + .priv2 = priv2, + }; + + iterate_skbuff_frag(iter->skb, &ctx, iter->iov_offset, len, 0); + + iter->iov_offset += ctx.progress; + iter->count -= ctx.progress; + return ctx.progress; +} + /* * Out of line iteration for iterator types that don't need such fast handling. */ @@ -2463,6 +2582,8 @@ size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_iterlist(iter, len, priv, priv2, ustep, step); if (iov_iter_is_scatterlist(iter)) return iterate_scatterlist(iter, len, priv, priv2, step); + if (iov_iter_is_skbuff(iter)) + return iterate_skbuff(iter, len, priv, priv2, step); WARN_ON(1); return 0; }