linux-toradex.git/fs/btrfs/sysfs.h, branch v6.7

btrfs: sysfs: update fs features directory asynchronously

2023-02-13T16:50:35+00:00

[BUG]
Since the introduction of per-fs feature sysfs interface
(/sys/fs/btrfs//features/), the content of that directory is never
updated.

Thus for the following case, that directory will not show the new
features like RAID56:

  # mkfs.btrfs -f $dev1 $dev2 $dev3
  # mount $dev1 $mnt
  # btrfs balance start -f -mconvert=raid5 $mnt
  # ls /sys/fs/btrfs/$uuid/features/
  extended_iref  free_space_tree  no_holes  skinny_metadata

While after unmount and mount, we got the correct features:

  # umount $mnt
  # mount $dev1 $mnt
  # ls /sys/fs/btrfs/$uuid/features/
  extended_iref  free_space_tree  no_holes  raid56 skinny_metadata

[CAUSE]
Because we never really try to update the content of per-fs features/
directory.

We had an attempt to update the features directory dynamically in commit
14e46e04958d ("btrfs: synchronize incompat feature bits with sysfs
files"), but unfortunately it get reverted in commit e410e34fad91
("Revert "btrfs: synchronize incompat feature bits with sysfs files"").
The problem in the original patch is, in the context of
btrfs_create_chunk(), we can not afford to update the sysfs group.

The exported but never utilized function, btrfs_sysfs_feature_update()
is the leftover of such attempt.  As even if we go sysfs_update_group(),
new files will need extra memory allocation, and we have no way to
specify the sysfs update to go GFP_NOFS.

[FIX]
This patch will address the old problem by doing asynchronous sysfs
update in the cleaner thread.

This involves the following changes:

- Make __btrfs_(set|clear)_fs_(incompat|compat_ro) helpers to set
  BTRFS_FS_FEATURE_CHANGED flag when needed

- Update btrfs_sysfs_feature_update() to use sysfs_update_group()
  And drop unnecessary arguments.

- Call btrfs_sysfs_feature_update() in cleaner_kthread
  If we have the BTRFS_FS_FEATURE_CHANGED flag set.

- Wake up cleaner_kthread in btrfs_commit_transaction if we have
  BTRFS_FS_FEATURE_CHANGED flag

By this, all the previously dangerous call sites like
btrfs_create_chunk() need no new changes, as above helpers would
have already set the BTRFS_FS_FEATURE_CHANGED flag.

The real work happens at cleaner_kthread, thus we pay the cost of
delaying the update to sysfs directory, but the delayed time should be
small enough that end user can not distinguish though it might get
delayed if the cleaner thread is busy with removing subvolumes or
defrag.

CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Anand Jain 
Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: split and refactor btrfs_sysfs_remove_devices_dir

2020-10-07T10:12:21+00:00

Similar to btrfs_sysfs_add_devices_dir()'s refactoring, split
btrfs_sysfs_remove_devices_dir() so that we don't have to use the device
argument to indicate whether to free all devices or just one device.

Export btrfs_sysfs_remove_device() as device operations outside of
sysfs.c now calls this instead of btrfs_sysfs_remove_devices_dir().

btrfs_sysfs_remove_devices_dir() is renamed to
btrfs_sysfs_remove_fs_devices() to suite its new role.

Now, no one outside of sysfs.c calls btrfs_sysfs_remove_fs_devices()
so it is redeclared s static. And the same function had to be moved
before its first caller.

Reviewed-by: Nikolay Borisov 
Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: simplify parameters of btrfs_sysfs_add_devices_dir

2020-10-07T10:12:21+00:00

When we add a device we need to add it to sysfs, so instead of using the
btrfs_sysfs_add_devices_dir() fs_devices argument to specify whether to
add a device or all of fs_devices, call the helper function directly
btrfs_sysfs_add_device() and thus make it non-static.

Reviewed-by: Nikolay Borisov 
Reviewed-by: Josef Bacik 
Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: make btrfs_sysfs_remove_devices_dir return void

2020-10-07T10:12:21+00:00

btrfs_sysfs_remove_devices_dir() return value is unused declare it as
void.

Reviewed-by: Nikolay Borisov 
Reviewed-by: Josef Bacik 
Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: remove const from btrfs_feature_set_name

2020-10-07T10:06:55+00:00

The function btrfs_feature_set_name returns a const char pointer, the
second const is not necessary and reported as a warning:

 In file included from fs/btrfs/space-info.c:6:
 fs/btrfs/sysfs.h:16:1: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
    16 | const char * const btrfs_feature_set_name(enum btrfs_feature_set set);
       | ^~~~~

Reviewed-by: Josef Bacik 
Signed-off-by: David Sterba

btrfs: remove fsid argument from btrfs_sysfs_update_sprout_fsid

2020-10-07T10:06:50+00:00

It can be accessed from 'fs_devices' as it's identical to
fs_info->fs_devices. Also add a comment about why we are calling the
function. No semantic changes.

Reviewed-by: Josef Bacik 
Reviewed-by: Johannes Thumshirn 
Reviewed-by: Anand Jain 
Signed-off-by: Nikolay Borisov 
Signed-off-by: David Sterba

btrfs: qgroup: export qgroups in sysfs

2020-07-27T10:55:37+00:00

This patch will add the following sysfs interface:

  /sys/fs/btrfs//qgroups//referenced
  /sys/fs/btrfs//qgroups//exclusive
  /sys/fs/btrfs//qgroups//max_referenced
  /sys/fs/btrfs//qgroups//max_exclusive
  /sys/fs/btrfs//qgroups//limit_flags

Which is also available in output of "btrfs qgroup show".

  /sys/fs/btrfs//qgroups//rsv_data
  /sys/fs/btrfs//qgroups//rsv_meta_pertrans
  /sys/fs/btrfs//qgroups//rsv_meta_prealloc

The last 3 rsv related members are not visible to users, but can be very
useful to debug qgroup limit related bugs.

Also, to avoid '/' used in , the separator between qgroup
level and qgroup id is changed to '_'.

The interface is not hidden behind 'debug' as we want this interface to
be included into production build and to provide another way to read the
qgroup information besides the ioctls.

Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: sysfs, rename device_link add/remove functions

2020-03-23T16:01:35+00:00

Since commit 668e48af7a94 ("btrfs: sysfs, add devid/dev_state kobject and
device attributes"), the functions btrfs_sysfs_add_device_link() and
btrfs_sysfs_rm_device_link() do more than just adding and removing the
device link as its name indicated. Rename them to be more specific
that's about the directory with the attirbutes

Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: sysfs, add devid/dev_state kobject and device attributes

2020-01-23T16:24:36+00:00

New sysfs attributes that track the filesystem status of devices, stored
in the per-filesystem directory in /sys/fs/btrfs/FSID/devinfo . There's
a directory for each device, with name corresponding to the numerical
device id.

  in_fs_metadata    - device is in the list of fs metadata
  missing           - device is missing (no device node or block device)
  replace_target    - device is target of replace
  writeable         - writes from fs are allowed

These attributes reflect the state of the device::dev_state and created
at mount time.

Sample output:
  $ pwd
   /sys/fs/btrfs/6e1961f1-5918-4ecc-a22f-948897b409f7/devinfo/1/
  $ ls
    in_fs_metadata  missing  replace_target  writeable
  $ cat missing
    0

The output from these attributes are 0 or 1. 0 indicates unset and 1
indicates set.  These attributes are readonly.

It is observed that the device delete thread and sysfs read thread will
not race because the delete thread calls sysfs kobject_put() which in
turn waits for existing sysfs read to complete.

Note for device replace devid swap:

During the replace the target device temporarily assumes devid 0 before
assigning the devid of the soruce device.

In btrfs_dev_replace_finishing() we remove source sysfs devid using the
function btrfs_sysfs_remove_devices_attr(), so after that call
kobject_rename() to update the devid in the sysfs.  This adds and calls
btrfs_sysfs_update_devid() helper function to update the device id.

Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
[ update changelog ]
Signed-off-by: David Sterba

btrfs: sysfs, merge btrfs_sysfs_add devices_kobj and fsid

2020-01-20T15:40:50+00:00

Merge btrfs_sysfs_add_fsid() and btrfs_sysfs_add_devices_kobj() functions
as these two are small and they are called one after the other.

Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba