From 9c8493d3a6d2e4d879d1ef67ff1abebd532c87a0 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 16 Jul 2021 16:51:34 -0400 Subject: [PATCH 18/43] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 RH-Author: Miroslav Rezanina RH-Bugzilla: 1957194 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 (cherry picked from commit 18473467d55a20d643b6c9b3a52de42f705b4d35) Signed-off-by: Danilo C. L. de Paula Signed-off-by: Miroslav Rezanina --- block/file-posix.c | 57 +++++++++++++++++++++++++++------------------- 1 file changed, 33 insertions(+), 24 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 44325a635d..7b4ebf65d5 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1173,22 +1173,27 @@ 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]; @@ -1197,26 +1202,20 @@ 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; @@ -1253,23 +1252,33 @@ out: static void raw_refresh_limits(BlockDriverState *bs, Error **errp) { BDRVRawState *s = bs->opaque; + struct stat st; - if (bs->sg) { - int ret = sg_get_max_transfer_length(s->fd); + 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 = pow2floor(ret); + bs->bl.max_hw_transfer = ret; } - ret = sg_get_max_segments(s->fd); + ret = hdev_get_max_segments(s->fd, &st); if (ret > 0) { bs->bl.max_iov = ret; } } - - 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); } static int check_for_dasd(int fd) -- 2.27.0