[PATCH 2/2] btrfs-progs: read fsid from the sysfs in device_is_seed
From: Anand Jain <hidden>
Date: 2021-10-19 00:24:09
Subsystem:
the rest · Maintainer:
Linus Torvalds
The kernel patch [1] added a sysfs interface to read the device fsid from the kernel, which is a better way to know the fsid of the device (rather than reading the superblock). It also works if in case the device is missing. Furthermore, the sysfs interface is readable from the non-root user. So use this new sysfs interface here to read the fsid. [1] btrfs: sysfs add devinfo/fsid to retrieve fsid from the device Signed-off-by: Anand Jain <redacted> --- cmds/filesystem-usage.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-)
diff --git a/cmds/filesystem-usage.c b/cmds/filesystem-usage.c
index 0dfc798e8dcc..f658c27b9609 100644
--- a/cmds/filesystem-usage.c
+++ b/cmds/filesystem-usage.c@@ -40,6 +40,7 @@ #include "common/help.h" #include "common/device-utils.h" #include "common/open-utils.h" +#include "common/path-utils.h" /* * Add the chunk info to the chunk_info list
@@ -706,14 +707,33 @@ out: return ret; } -static int device_is_seed(const char *dev_path, u8 *mnt_fsid) +static int device_is_seed(int fd, const char *dev_path, u64 devid, u8 *mnt_fsid) { + char fsidparse[BTRFS_UUID_UNPARSED_SIZE]; + char fsid_path[PATH_MAX]; + char devid_str[20]; uuid_t fsid; - int ret; + int ret = -1; + int sysfs_fd; + + snprintf(devid_str, 20, "%llu", devid); + /* devinfo/<devid>/fsid */ + path_cat3_out(fsid_path, "devinfo", devid_str, "fsid"); + + /* /sys/fs/btrfs/<fsid>/devinfo/<devid>/fsid */ + sysfs_fd = sysfs_open_fsid_file(fd, fsid_path); + if (sysfs_fd >= 0) { + sysfs_read_file(sysfs_fd, fsidparse, BTRFS_UUID_UNPARSED_SIZE); + fsidparse[BTRFS_UUID_UNPARSED_SIZE - 1] = 0; + ret = uuid_parse(fsidparse, fsid); + close(sysfs_fd); + } - ret = dev_to_fsid(dev_path, fsid); - if (ret) - return ret; + if (ret) { + ret = dev_to_fsid(dev_path, fsid); + if (ret) + return ret; + } if (memcmp(mnt_fsid, fsid, BTRFS_FSID_SIZE)) return 0;
@@ -768,13 +788,15 @@ static int load_device_info(int fd, struct device_info **device_info_ptr, } /* - * Skip seed device by checking device's fsid (requires root). - * And we will skip only if dev_to_fsid is successful and dev + * Skip seed device by checking device's fsid (requires root if + * kernel is not patched to provide fsid from the sysfs). + * And we will skip only if device_is_seed is successful and dev * is a seed device. * Ignore any other error including -EACCES, which is seen when * a non-root process calls dev_to_fsid(path)->open(path). */ - ret = device_is_seed((const char *)dev_info.path, fi_args.fsid); + ret = device_is_seed(fd, (const char *)dev_info.path, i, + fi_args.fsid); if (!ret) continue;
--
2.31.1