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[PATCH 2/3] file-posix: try BLKSECTGET on block devices too, do not roun
From: |
Paolo Bonzini |
Subject: |
[PATCH 2/3] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 |
Date: |
Thu, 15 Apr 2021 14:43:06 +0200 |
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 for /dev/sgN devices and sectors 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>
---
block/file-posix.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index 9e316a2a97..e37a6bb8de 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1173,13 +1173,13 @@ static void raw_reopen_abort(BDRVReopenState *state)
s->reopen_state = NULL;
}
-static int sg_get_max_transfer_length(int fd)
+static int sg_get_max_transfer_length(int fd, struct stat *st)
{
#ifdef BLKSECTGET
int max_bytes = 0;
if (ioctl(fd, BLKSECTGET, &max_bytes) == 0) {
- return max_bytes;
+ return S_ISBLK(st->st_mode) ? max_bytes * 512 : max_bytes;
} else {
return -errno;
}
@@ -1188,7 +1188,7 @@ static int sg_get_max_transfer_length(int fd)
#endif
}
-static int sg_get_max_segments(int fd)
+static int sg_get_max_segments(int fd, struct stat *st)
{
#ifdef CONFIG_LINUX
char buf[32];
@@ -1197,15 +1197,9 @@ 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;
- }
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;
@@ -1242,15 +1236,20 @@ out:
static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
{
BDRVRawState *s = bs->opaque;
+ struct stat st;
+
+ if (fstat(s->fd, &st)) {
+ return;
+ }
- if (bs->sg) {
- int ret = sg_get_max_transfer_length(s->fd);
+ if (bs->sg || S_ISBLK(st.st_mode)) {
+ int ret = sg_get_max_transfer_length(s->fd, &st);
if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
- bs->bl.max_transfer = pow2floor(ret);
+ bs->bl.max_transfer = ret;
}
- ret = sg_get_max_segments(s->fd);
+ ret = sg_get_max_segments(s->fd, &st);
if (ret > 0) {
bs->bl.max_iov = ret;
}
--
2.30.1