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btrfs-progs: ignore devices representing paths in multipath

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Currently btrfs-progs will happily enumerate any device which has a
btrfs filesystem on it irrespective of its type. For the majority of
use cases that's fine and there haven't been any problems with that.
However, there was a recent report that in multipath scenario when
running "btrfs fi show" after a path flap (path going down and then
coming back up) instead of the multipath device being show the device
which represents the flapped path is shown. So a multipath filesystem
might look like:

  Label: none  uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
	  Total devices 1 FS bytes used 192.00KiB
	  devid    1 size 10.00GiB used 536.00MiB path /dev/mapper/3600140501cc1f49e5364f0093869c763

/dev/mapper/xxx is actually backed by an arbitrary number of paths,
which in turn are presented to the system as ordinary SCSI devices i.e
/dev/sdX. If a path flaps and a user re-runs 'btrfs fi show' the output
would look like:

  Label: none  uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
	  Total devices 1 FS bytes used 192.00KiB
	  devid    1 size 10.00GiB used 536.00MiB path /dev/sdd

This only occurs on unmounted filesystems as those are enumerated by
btrfs-progs, for mounted filesystem the kernel properly deals only with
the actual multipath device.

Turns out the output of this command is consumed by libraries and the
presence of a path device rather than the actual multipath causes
issues.

Fix this by checking for the presence of DM_MULTIPATH_DEVICE_PATH
udev attribute as multipath path devices are tagged with this attribute
by the multipath udev scripts.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2021-09-30 15:06:33 +03:00 committed by David Sterba
parent f74ebeee5c
commit 681b4bd5e1
1 changed files with 47 additions and 0 deletions
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47
common/device-scan.c
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@ -14,6 +14,10 @@
* Boston, MA 021110-1307, USA.
*/
#ifdef STATIC_BUILD
#undef HAVE_LIBUDEV
#endif
#include "kerncompat.h"
#include <sys/ioctl.h>
#include <stdlib.h>
@ -25,6 +29,10 @@
#include <dirent.h>
#include <blkid/blkid.h>
#include <uuid/uuid.h>
#ifdef HAVE_LIBUDEV
#include <sys/stat.h>
#include <libudev.h>
#endif
#include "kernel-lib/overflow.h"
#include "common/path-utils.h"
#include "common/device-scan.h"
@ -364,6 +372,42 @@ void free_seen_fsid(struct seen_fsid *seen_fsid_hash[])
}
}
#ifdef HAVE_LIBUDEV
static bool is_path_device(char *device_path)
{
struct udev *udev = NULL;
struct udev_device *dev = NULL;
struct stat dev_stat;
const char *val;
bool ret = false;
if (stat(device_path, &dev_stat) < 0)
return false;
udev = udev_new();
if (!udev)
goto out;
dev = udev_device_new_from_devnum(udev, 'b', dev_stat.st_rdev);
if (!dev)
goto out;
val = udev_device_get_property_value(dev, "DM_MULTIPATH_DEVICE_PATH");
if (val && atoi(val) > 0)
ret = true;
out:
udev_device_unref(dev);
udev_unref(udev);
return ret;
}
#else
static bool is_path_device(char *device_path)
{
return false;
}
#endif
int btrfs_scan_devices(int verbose)
{
int fd = -1;
@ -394,6 +438,9 @@ int btrfs_scan_devices(int verbose)
/* if we are here its definitely a btrfs disk*/
strncpy_null(path, blkid_dev_devname(dev));
if (is_path_device(path))
continue;
fd = open(path, O_RDONLY);
if (fd < 0) {
error("cannot open %s: %m", path);