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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744902341; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PRGelV8grg7PhxNQDzoDLvMsEhM8cB8/GRHCfaYnCb4=; b=gr+5rJJ4+0bP8ETV9YMb3MRbjh9eWIDG7Oh2C61dG7UwSqG9sBYSiFPhdZ5t79t6JR8Fsf M97UT558Q62zXy4tkLMqAySLpg0l9R/oUkvlPhVfd4ChiSGFtWmIyfctqZTEaU473lBsbx LYtIFrfV4PbXejXF0YGpPkBgcHyHEIk= X-MC-Unique: xaXB4f8EPbSWbfGwKG7noA-1 X-Mimecast-MFC-AGG-ID: xaXB4f8EPbSWbfGwKG7noA_1744902335 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Stefan Hajnoczi , Fam Zheng , Hanna Reitz , Kevin Wolf Subject: [PATCH v4 1/2] file-posix: probe discard alignment on Linux block devices Date: Thu, 17 Apr 2025 11:05:27 -0400 Message-ID: <20250417150528.76470-2-stefanha@redhat.com> In-Reply-To: <20250417150528.76470-1-stefanha@redhat.com> References: <20250417150528.76470-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Populate the pdiscard_alignment block limit so the block layer is able align discard requests correctly. Signed-off-by: Stefan Hajnoczi --- block/file-posix.c | 67 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 66 insertions(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index 56d1972d15..0d6e12f880 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1276,10 +1276,10 @@ static int get_sysfs_zoned_model(struct stat *st, B= lockZoneModel *zoned) } #endif /* defined(CONFIG_BLKZONED) */ =20 +#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 =3D NULL; @@ -1299,6 +1299,30 @@ static long get_sysfs_long_val(struct stat *st, cons= t 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 =3D NULL; + const char *end; + unsigned int val; + int ret; + + ret =3D get_sysfs_str_val(st, attribute, &str); + if (ret < 0) { + return ret; + } + + /* The file is ended with '\n', pass 'end' to accept that. */ + ret =3D qemu_strtoui(str, &end, 10, &val); + if (ret =3D=3D 0 && end && *end =3D=3D '\0') { + *u32 =3D val; + } + return ret; +} #endif =20 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 } =20 +/* + * 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) } } =20 + if (S_ISBLK(st.st_mode)) { + uint32_t dalign =3D 0; + int ret; + + ret =3D hdev_get_pdiscard_alignment(&st, &dalign); + if (ret =3D=3D 0) { + uint32_t ralign =3D bs->bl.request_alignment; + + /* Probably never happens, but handle it just in case */ + if (dalign < ralign && (ralign % dalign =3D=3D 0)) { + dalign =3D ralign; + } + + /* The block layer requires a multiple of request_alignment */ + if (dalign % ralign !=3D 0) { + error_setg(errp, "Invalid pdiscard_alignment limit %u is n= ot a " + "multiple of request_alignment %u", dalign, ralign= ); + return; + } + + bs->bl.pdiscard_alignment =3D dalign; + } + } + raw_refresh_zoned_limits(bs, &st, errp); } =20 --=20 2.49.0