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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b422b7b2700sm12465778a12.15.2025.08.05.20.59.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 20:59:09 -0700 (PDT) Message-ID: Date: Wed, 6 Aug 2025 13:29:05 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs-progs: Fix get_partition_sector_size_sysfs() to handle loopback and device mapper devices To: Zoltan Racz , linux-btrfs@vger.kernel.org References: <20250801110318.37249-1-racz.zoli@gmail.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20250801110318.37249-1-racz.zoli@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/8/1 20:33, Zoltan Racz 写道: > Commit e39ed66 added get_partition_sector_size_sysfs() used by "btrfs device usage" > which returns the sector size of a partition (or its parent). After more testing > it turned out it couldn`t handle loopback or mapper devices. This patch adds a fix > for them. After more digging into the sysfs implementation and how util-linux is handling the sysfs block device size, it turns out that /sys/block//size is always in sector unit (512 bytes). It's not related to any block size in the queue directory. The core code implementing this is from block/genhd.c, function part_size_show(): sysfs_emit(buf, "%llu\n", bdev_nr_sectors(dev_to_bdev(dev)); BTW, to my surprise, this very basic member is not explained in any sysfs related docs... So we don't need all those complex workaround at all, just a simple shift with SECTOR_SHIFT will solve the problem. I'll update your previous fix to use /sys/block//size with left shift directly. Thanks, Qu > > Signed-off-by: Zoltan Racz > --- > common/device-utils.c | 48 +++++++++++++++++++++++++++++-------------- > 1 file changed, 33 insertions(+), 15 deletions(-) > > diff --git a/common/device-utils.c b/common/device-utils.c > index dd781bc5..a75194bf 100644 > --- a/common/device-utils.c > +++ b/common/device-utils.c > @@ -353,26 +353,44 @@ static ssize_t get_partition_sector_size_sysfs(const char *name) > char sysfs[PATH_MAX] = {}; > char sizebuf[128]; > > - snprintf(link_path, PATH_MAX, "/sys/class/block/%s/..", name); > + /* > + * First we look for hw_sector_size directly directly under > + * /sys/class/block/[partition_name]/queue. In case of loopback and > + * device mapper devices there is no parent device (like /dev/sda1 -> /dev/sda), > + * and the partition`s sysfs folder itself contains informations regarding > + * the sector size > + */ > + snprintf(sysfs, PATH_MAX, "/sys/class/block/%s/queue/hw_sector_size", name); > + sysfd = open(sysfs, O_RDONLY); > > - if (!realpath(link_path, real_path)) { > - error("Failed to resolve realpath of %s: %s\n", link_path, strerror(errno)); > - return -1; > - } > + if (sysfd < 0) { > + /* > + * If we couldn`t find it, it means our partition is created on a real > + * device and we need to find its parent > + */ > + snprintf(link_path, PATH_MAX, "/sys/class/block/%s/..", name); > > - dev_name = basename(real_path); > + if (!realpath(link_path, real_path)) { > + error("Failed to resolve realpath of %s: %s\n", link_path, strerror(errno)); > + return -1; > + } > > - if (!dev_name) { > - error("Failed to determine basename for path %s\n", real_path); > - return -1; > - } > + dev_name = basename(real_path); > > - snprintf(sysfs, PATH_MAX, "/sys/class/block/%s/queue/hw_sector_size", dev_name); > + if (!dev_name) { > + error("Failed to determine basename for path %s\n", real_path); > + return -1; > + } > > - sysfd = open(sysfs, O_RDONLY); > - if (sysfd < 0) { > - error("Error opening %s to determine dev sector size: %s\n", real_path, strerror(errno)); > - return -1; > + memset(sysfs, 0, PATH_MAX); > + snprintf(sysfs, PATH_MAX, "/sys/class/block/%s/queue/hw_sector_size", dev_name); > + > + sysfd = open(sysfs, O_RDONLY); > + > + if (sysfd < 0) { > + error("Error opening %s to determine dev sector size: %s\n", real_path, strerror(errno)); > + return -1; > + } > } > > ret = sysfs_read_file(sysfd, sizebuf, sizeof(sizebuf));