From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Cc: kwolf@redhat.com, qemu-block@nongnu.org
Subject: [PATCH v3 4/7] file-posix: try BLKSECTGET on block devices too, do not round to power of 2
Date: Thu, 3 Jun 2021 15:37:19 +0200 [thread overview]
Message-ID: <20210603133722.218465-5-pbonzini@redhat.com> (raw)
In-Reply-To: <20210603133722.218465-1-pbonzini@redhat.com>
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.
This patch reintroduces the logic that was removed in commit 867eccfed8
("file-posix: Use max transfer length/segment count only for SCSI
passthrough", 2019-07-12). The removal was motivated by the performance
regression when using a block device's max_transfer with kernel I/O;
the new, separate max_hw_transfer limit avoids reintroducing the same
regression.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
block/file-posix.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index f55f92d0f5..1439293f63 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1149,22 +1149,27 @@ 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];
@@ -1173,12 +1178,6 @@ 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 (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
@@ -1192,7 +1191,7 @@ static int sg_get_max_segments(int fd)
}
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;
@@ -1229,15 +1228,20 @@ 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 = 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;
}
--
2.31.1
next prev parent reply other threads:[~2021-06-03 13:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-03 13:37 [PATCH v3 0/7] block: file-posix queue Paolo Bonzini
2021-06-03 13:37 ` [PATCH v3 1/7] file-posix: fix max_iov for /dev/sg devices Paolo Bonzini
2021-06-07 5:39 ` Vladimir Sementsov-Ogievskiy
2021-06-07 6:16 ` Vladimir Sementsov-Ogievskiy
2021-06-07 7:23 ` Vladimir Sementsov-Ogievskiy
2021-06-15 15:58 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 2/7] scsi-generic: pass max_segments via max_iov field in BlockLimits Paolo Bonzini
2021-06-15 16:06 ` Max Reitz
2021-06-15 16:20 ` Max Reitz
2021-06-15 17:41 ` Paolo Bonzini
2021-06-03 13:37 ` [PATCH v3 3/7] block: add max_hw_transfer to BlockLimits Paolo Bonzini
2021-06-03 17:33 ` Eric Blake
2021-06-04 7:21 ` Paolo Bonzini
2021-06-15 16:18 ` Max Reitz
2021-06-16 13:18 ` Paolo Bonzini
2021-06-16 13:46 ` Max Reitz
2021-06-17 9:59 ` Paolo Bonzini
2021-06-03 13:37 ` Paolo Bonzini [this message]
2021-06-15 16:32 ` [PATCH v3 4/7] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 Max Reitz
2021-06-03 13:37 ` [PATCH v3 5/7] block: feature detection for host block support Paolo Bonzini
2021-06-15 16:40 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 6/7] block: check for sys/disk.h Paolo Bonzini
2021-06-15 16:42 ` Max Reitz
2021-06-03 13:37 ` [PATCH v3 7/7] block: detect DKIOCGETBLOCKCOUNT/SIZE before use Paolo Bonzini
2021-06-15 16:50 ` Max Reitz
2021-06-15 16:57 ` Daniel P. Berrangé
2021-06-07 13:52 ` [PATCH v3 0/7] block: file-posix queue Maxim Levitsky
2021-06-10 13:40 ` Paolo Bonzini
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