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btrfs-progs: read fsid from the sysfs in device_is_seed 

The kernel commit a26d60dedf9a ("btrfs: sysfs: add devinfo/fsid to
retrieve actual fsid from the device") introduced a sysfs interface
to access the device's fsid from the userspace. This is a more
reliable method to obtain the fsid compared to reading the
superblock, and it even works if the device is not present.
Additionally, this sysfs interface can be read by non-root users.

Therefore, it is recommended to utilize this new sysfs interface to
retrieve the fsid.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Anand Jain 2023-02-13 17:37:42 +08:00 committed by David Sterba
parent bdd0ca8a9a
commit 32c2e57c65
1 changed files with 31 additions and 7 deletions
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34
cmds/filesystem-usage.c
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@ -27,6 +27,7 @@
#include <fcntl.h>
#include <dirent.h>
#include <limits.h>
#include <uuid/uuid.h>
#include "kernel-lib/sizes.h"
#include "kernel-shared/ctree.h"
#include "kernel-shared/disk-io.h"
@ -38,6 +39,7 @@
#include "common/help.h"
#include "common/device-utils.h"
#include "common/messages.h"
#include "common/path-utils.h"
#include "cmds/filesystem-usage.h"
#include "cmds/commands.h"
@ -700,14 +702,35 @@ out:
return ret;
}
static int device_is_seed(const char *dev_path, const u8 *mnt_fsid)
static int device_is_seed(int fd, const char *dev_path, u64 devid, const u8 *mnt_fsid)
{
char fsid_str[BTRFS_UUID_UNPARSED_SIZE];
char fsid_path[PATH_MAX];
char devid_str[20];
u8 fsid[BTRFS_UUID_SIZE];
int ret;
int ret = -1;
int sysfs_fd;
snprintf(devid_str, 20, "%llu", devid);
/* devinfo/<devid>/fsid */
ret = path_cat3_out(fsid_path, "devinfo", devid_str, "fsid");
if (ret < 0)
return ret;
/* /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, fsid_str, BTRFS_UUID_UNPARSED_SIZE);
fsid_str[BTRFS_UUID_UNPARSED_SIZE - 1] = 0;
ret = uuid_parse(fsid_str, fsid);
close(sysfs_fd);
}
if (ret) {
ret = dev_to_fsid(dev_path, fsid);
if (ret)
return ret;
}
if (memcmp(mnt_fsid, fsid, BTRFS_FSID_SIZE) != 0)
return 0;
@ -762,13 +785,14 @@ static int load_device_info(int fd, struct device_info **devinfo_ret,
}
/*
* 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;