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Fri, 25 Jun 2021 07:18:41 -0700 (PDT) Received: from avogadro.lan ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id c28sm326579ejc.102.2021.06.25.07.18.41 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jun 2021 07:18:41 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 18/28] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 Date: Fri, 25 Jun 2021 16:18:12 +0200 Message-Id: <20210625141822.1368639-19-pbonzini@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210625141822.1368639-1-pbonzini@redhat.com> References: <20210625141822.1368639-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::634; envelope-from=paolo.bonzini@gmail.com; helo=mail-ej1-x634.google.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.25, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" bs->sg is only true for character devices, but block devices can also be used with scsi-block and scsi-generic. Unfortunately BLKSECTGET returns bytes in an int for /dev/sgN devices, and sectors in a short for block devices, so account for that in the code. The maximum transfer also need not be a power of 2 (for example I have seen disks with 1280 KiB maximum transfer) so there's no need to pass the result through pow2floor. Signed-off-by: Paolo Bonzini --- block/file-posix.c | 67 ++++++++++++++++++++++++++-------------------- 1 file changed, 38 insertions(+), 29 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 88e58d2863..ea102483b0 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1147,22 +1147,27 @@ static void raw_reopen_abort(BDRVReopenState *state) s->reopen_state = NULL; } -static int sg_get_max_transfer_length(int fd) +static int hdev_get_max_hw_transfer(int fd, struct stat *st) { #ifdef BLKSECTGET - int max_bytes = 0; - - if (ioctl(fd, BLKSECTGET, &max_bytes) == 0) { - return max_bytes; + if (S_ISBLK(st->st_mode)) { + unsigned short max_sectors = 0; + if (ioctl(fd, BLKSECTGET, &max_sectors) == 0) { + return max_sectors * 512; + } } else { - return -errno; + int max_bytes = 0; + if (ioctl(fd, BLKSECTGET, &max_bytes) == 0) { + return max_bytes; + } } + return -errno; #else return -ENOSYS; #endif } -static int sg_get_max_segments(int fd) +static int hdev_get_max_segments(int fd, struct stat *st) { #ifdef CONFIG_LINUX char buf[32]; @@ -1171,26 +1176,20 @@ static int sg_get_max_segments(int fd) int ret; int sysfd = -1; long max_segments; - struct stat st; - if (fstat(fd, &st)) { - ret = -errno; - goto out; - } - - if (S_ISCHR(st.st_mode)) { + if (S_ISCHR(st->st_mode)) { if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) { return ret; } return -ENOTSUP; } - if (!S_ISBLK(st.st_mode)) { + if (!S_ISBLK(st->st_mode)) { return -ENOTSUP; } sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments", - major(st.st_rdev), minor(st.st_rdev)); + major(st->st_rdev), minor(st->st_rdev)); sysfd = open(sysfspath, O_RDONLY); if (sysfd == -1) { ret = -errno; @@ -1227,23 +1226,33 @@ out: static void raw_refresh_limits(BlockDriverState *bs, Error **errp) { BDRVRawState *s = bs->opaque; - - if (bs->sg) { - int ret = sg_get_max_transfer_length(s->fd); - - if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { - bs->bl.max_hw_transfer = pow2floor(ret); - } - - ret = sg_get_max_segments(s->fd); - if (ret > 0) { - bs->bl.max_iov = ret; - } - } + struct stat st; raw_probe_alignment(bs, s->fd, errp); bs->bl.min_mem_alignment = s->buf_align; bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size); + + /* + * Maximum transfers are best effort, so it is okay to ignore any + * errors. That said, based on the man page errors in fstat would be + * very much unexpected; the only possible case seems to be ENOMEM. + */ + if (fstat(s->fd, &st)) { + return; + } + + if (bs->sg || S_ISBLK(st.st_mode)) { + int ret = hdev_get_max_hw_transfer(s->fd, &st); + + if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { + bs->bl.max_hw_transfer = ret; + } + + ret = hdev_get_max_segments(s->fd, &st); + if (ret > 0) { + bs->bl.max_iov = ret; + } + } } static int check_for_dasd(int fd) -- 2.31.1