From cc31f7eb1c362dc308a163b7364c96ed098a793a Mon Sep 17 00:00:00 2001 From: Hanna Czenczek Date: Tue, 11 Apr 2023 19:34:17 +0200 Subject: [PATCH 3/5] util/iov: Remove qemu_iovec_init_extended() RH-Author: Hanna Czenczek RH-MergeRequest: 291: block: Split padded I/O vectors exceeding IOV_MAX RH-Bugzilla: 2141964 RH-Acked-by: Emanuele Giuseppe Esposito RH-Acked-by: Stefan Hajnoczi RH-Commit: [3/5] 19c8307ef1289f1991199d1d1f6ab6c89a4b59ce bdrv_pad_request() was the main user of qemu_iovec_init_extended(). HEAD^ has removed that use, so we can remove qemu_iovec_init_extended() now. The only remaining user is qemu_iovec_init_slice(), which can easily inline the small part it really needs. Note that qemu_iovec_init_extended() offered a memcpy() optimization to initialize the new I/O vector. qemu_iovec_concat_iov(), which is used to replace its functionality, does not, but calls qemu_iovec_add() for every single element. If we decide this optimization was important, we will need to re-implement it in qemu_iovec_concat_iov(), which might also benefit its pre-existing users. Reviewed-by: Eric Blake Reviewed-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Hanna Czenczek Message-Id: <20230411173418.19549-4-hreitz@redhat.com> (cherry picked from commit cc63f6f6fa1aaa4b6405dd69432c693e9c8d18ca) Signed-off-by: Hanna Czenczek --- include/qemu/iov.h | 5 --- util/iov.c | 79 +++++++--------------------------------------- 2 files changed, 11 insertions(+), 73 deletions(-) diff --git a/include/qemu/iov.h b/include/qemu/iov.h index 46fadfb27a..63a1c01965 100644 --- a/include/qemu/iov.h +++ b/include/qemu/iov.h @@ -222,11 +222,6 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov) void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint); void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov); -int qemu_iovec_init_extended( - QEMUIOVector *qiov, - void *head_buf, size_t head_len, - QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len, - void *tail_buf, size_t tail_len); void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source, size_t offset, size_t len); struct iovec *qemu_iovec_slice(QEMUIOVector *qiov, diff --git a/util/iov.c b/util/iov.c index 3ccb530b16..af3ccc2546 100644 --- a/util/iov.c +++ b/util/iov.c @@ -411,70 +411,6 @@ int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len) return niov; } -/* - * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov, - * and @tail_buf buffer into new qiov. - */ -int qemu_iovec_init_extended( - QEMUIOVector *qiov, - void *head_buf, size_t head_len, - QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len, - void *tail_buf, size_t tail_len) -{ - size_t mid_head, mid_tail; - int total_niov, mid_niov = 0; - struct iovec *p, *mid_iov = NULL; - - assert(mid_qiov->niov <= IOV_MAX); - - if (SIZE_MAX - head_len < mid_len || - SIZE_MAX - head_len - mid_len < tail_len) - { - return -EINVAL; - } - - if (mid_len) { - mid_iov = qemu_iovec_slice(mid_qiov, mid_offset, mid_len, - &mid_head, &mid_tail, &mid_niov); - } - - total_niov = !!head_len + mid_niov + !!tail_len; - if (total_niov > IOV_MAX) { - return -EINVAL; - } - - if (total_niov == 1) { - qemu_iovec_init_buf(qiov, NULL, 0); - p = &qiov->local_iov; - } else { - qiov->niov = qiov->nalloc = total_niov; - qiov->size = head_len + mid_len + tail_len; - p = qiov->iov = g_new(struct iovec, qiov->niov); - } - - if (head_len) { - p->iov_base = head_buf; - p->iov_len = head_len; - p++; - } - - assert(!mid_niov == !mid_len); - if (mid_niov) { - memcpy(p, mid_iov, mid_niov * sizeof(*p)); - p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head; - p[0].iov_len -= mid_head; - p[mid_niov - 1].iov_len -= mid_tail; - p += mid_niov; - } - - if (tail_len) { - p->iov_base = tail_buf; - p->iov_len = tail_len; - } - - return 0; -} - /* * Check if the contents of subrange of qiov data is all zeroes. */ @@ -506,14 +442,21 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes) void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source, size_t offset, size_t len) { - int ret; + struct iovec *slice_iov; + int slice_niov; + size_t slice_head, slice_tail; assert(source->size >= len); assert(source->size - len >= offset); - /* We shrink the request, so we can't overflow neither size_t nor MAX_IOV */ - ret = qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0); - assert(ret == 0); + slice_iov = qemu_iovec_slice(source, offset, len, + &slice_head, &slice_tail, &slice_niov); + if (slice_niov == 1) { + qemu_iovec_init_buf(qiov, slice_iov[0].iov_base + slice_head, len); + } else { + qemu_iovec_init(qiov, slice_niov); + qemu_iovec_concat_iov(qiov, slice_iov, slice_niov, slice_head, len); + } } void qemu_iovec_destroy(QEMUIOVector *qiov) -- 2.39.3