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file-posix: try BLKSECTGET on block devices too, do not round to power of 2

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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 <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-04-14 19:52:26 +02:00
parent 24b36e9813
commit 18473467d5
1 changed files with 38 additions and 29 deletions
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67
block/file-posix.c
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@ -1147,22 +1147,27 @@ static void raw_reopen_abort(BDRVReopenState *state)
s->reopen_state = NULL; 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 #ifdef BLKSECTGET
int max_bytes = 0; if (S_ISBLK(st->st_mode)) {
unsigned short max_sectors = 0;
if (ioctl(fd, BLKSECTGET, &max_bytes) == 0) { if (ioctl(fd, BLKSECTGET, &max_sectors) == 0) {
return max_bytes; return max_sectors * 512;
}
} else { } else {
return -errno; int max_bytes = 0;
if (ioctl(fd, BLKSECTGET, &max_bytes) == 0) {
return max_bytes;
}
} }
return -errno;
#else #else
return -ENOSYS; return -ENOSYS;
#endif #endif
} }
static int sg_get_max_segments(int fd) static int hdev_get_max_segments(int fd, struct stat *st)
{ {
#ifdef CONFIG_LINUX #ifdef CONFIG_LINUX
char buf[32]; char buf[32];
@ -1171,26 +1176,20 @@ static int sg_get_max_segments(int fd)
int ret; int ret;
int sysfd = -1; int sysfd = -1;
long max_segments; long max_segments;
struct stat st;
if (fstat(fd, &st)) { if (S_ISCHR(st->st_mode)) {
ret = -errno;
goto out;
}
if (S_ISCHR(st.st_mode)) {
if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) { if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
return ret; return ret;
} }
return -ENOTSUP; return -ENOTSUP;
} }
if (!S_ISBLK(st.st_mode)) { if (!S_ISBLK(st->st_mode)) {
return -ENOTSUP; return -ENOTSUP;
} }
sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments", 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); sysfd = open(sysfspath, O_RDONLY);
if (sysfd == -1) { if (sysfd == -1) {
ret = -errno; ret = -errno;
@ -1227,23 +1226,33 @@ out:
static void raw_refresh_limits(BlockDriverState *bs, Error **errp) static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
{ {
BDRVRawState *s = bs->opaque; BDRVRawState *s = bs->opaque;
struct stat st;
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;
}
}
raw_probe_alignment(bs, s->fd, errp); raw_probe_alignment(bs, s->fd, errp);
bs->bl.min_mem_alignment = s->buf_align; bs->bl.min_mem_alignment = s->buf_align;
bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size); 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) static int check_for_dasd(int fd)