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file-posix: probe discard alignment on Linux block devices

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Populate the pdiscard_alignment block limit so the block layer is able
align discard requests correctly.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250417150528.76470-2-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2025-04-17 11:05:27 -04:00 • committed by Kevin Wolf
parent 019fbfa4bc
commit f605796aae
1 changed files with 66 additions and 1 deletions
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67
block/file-posix.c
View file

@ -1276,10 +1276,10 @@ static int get_sysfs_zoned_model(struct stat *st, BlockZoneModel *zoned)
}
#endif /* defined(CONFIG_BLKZONED) */
#ifdef CONFIG_LINUX
/*
* Get a sysfs attribute value as a long integer.
*/
#ifdef CONFIG_LINUX
static long get_sysfs_long_val(struct stat *st, const char *attribute)
{
g_autofree char *str = NULL;
@ -1299,6 +1299,30 @@ static long get_sysfs_long_val(struct stat *st, const char *attribute)
}
return ret;
}
/*
* Get a sysfs attribute value as a uint32_t.
*/
static int get_sysfs_u32_val(struct stat *st, const char *attribute,
uint32_t *u32)
{
g_autofree char *str = NULL;
const char *end;
unsigned int val;
int ret;
ret = get_sysfs_str_val(st, attribute, &str);
if (ret < 0) {
return ret;
}
/* The file is ended with '\n', pass 'end' to accept that. */
ret = qemu_strtoui(str, &end, 10, &val);
if (ret == 0 && end && *end == '\0') {
*u32 = val;
}
return ret;
}
#endif
static int hdev_get_max_segments(int fd, struct stat *st)
@ -1318,6 +1342,23 @@ static int hdev_get_max_segments(int fd, struct stat *st)
#endif
}
/*
* Fills in *dalign with the discard alignment and returns 0 on success,
* -errno otherwise.
*/
static int hdev_get_pdiscard_alignment(struct stat *st, uint32_t *dalign)
{
#ifdef CONFIG_LINUX
/*
* Note that Linux "discard_granularity" is QEMU "discard_alignment". Linux
* "discard_alignment" is something else.
*/
return get_sysfs_u32_val(st, "discard_granularity", dalign);
#else
return -ENOTSUP;
#endif
}
#if defined(CONFIG_BLKZONED)
/*
* If the reset_all flag is true, then the wps of zone whose state is
@ -1527,6 +1568,30 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
}
}
if (S_ISBLK(st.st_mode)) {
uint32_t dalign = 0;
int ret;
ret = hdev_get_pdiscard_alignment(&st, &dalign);
if (ret == 0) {
uint32_t ralign = bs->bl.request_alignment;
/* Probably never happens, but handle it just in case */
if (dalign < ralign && (ralign % dalign == 0)) {
dalign = ralign;
}
/* The block layer requires a multiple of request_alignment */
if (dalign % ralign != 0) {
error_setg(errp, "Invalid pdiscard_alignment limit %u is not a "
"multiple of request_alignment %u", dalign, ralign);
return;
}
bs->bl.pdiscard_alignment = dalign;
}
}
raw_refresh_zoned_limits(bs, &st, errp);
}