linux.git/fs/btrfs/sysfs.c, branch v5.6

btrfs: sysfs, move device id directories to UUID/devinfo

2020-02-12T17:28:22+00:00

Originally it was planned to create device id directories under
UUID/devinfo, but it got under UUID/devices by mistake. We really want
it under definfo so the bare device node names are not mixed with device
ids and are easy to enumerate.

Fixes: 668e48af7a94 ("btrfs: sysfs, add devid/dev_state kobject and device attributes")
Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: sysfs, add UUID/devinfo kobject

2020-02-12T17:28:18+00:00

Create directory /sys/fs/btrfs/UUID/devinfo to hold devices directories
by the id (unlike /devices).

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: keep track of discard reuse stats

2020-01-20T15:41:00+00:00

Keep track of how much we are discarding and how often we are reusing
with async discard. The discard_*_bytes values don't need any special
protection because the work item provides the single threaded access.

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

btrfs: make max async discard size tunable

2020-01-20T15:40:59+00:00

Expose max_discard_size as a tunable via sysfs and switch the current
fixed maximum to the default value.

Signed-off-by: Dennis Zhou 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: add kbps discard rate limit for async discard

2020-01-20T15:40:59+00:00

Provide the ability to rate limit based on kbps in addition to iops as
additional guides for the target discard rate. The delay used ends up
being max(kbps_delay, iops_delay).

Signed-off-by: Dennis Zhou 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: calculate discard delay based on number of extents

2020-01-20T15:40:59+00:00

An earlier patch keeps track of discardable_extents. These are
undiscarded extents managed by the free space cache. Here, we will use
this to dynamically calculate the discard delay interval.

There are 3 rate to consider. The first is the target convergence rate,
the rate to discard all discardable_extents over the
BTRFS_DISCARD_TARGET_MSEC time frame. This is clamped by the lower
limit, the iops limit or BTRFS_DISCARD_MIN_DELAY (1ms), and the upper
limit, BTRFS_DISCARD_MAX_DELAY (1s). We reevaluate this delay every
transaction commit.

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

btrfs: keep track of discardable_bytes for async discard

2020-01-20T15:40:59+00:00

Keep track of this metric so that we can understand how ahead or behind
we are in discarding rate. This uses the same accounting method as
discardable_extents, deltas between previous/current values and
propagating them up.

Signed-off-by: Dennis Zhou 
Reviewed-by: David Sterba 
[ update changelog ]
Signed-off-by: David Sterba

btrfs: track discardable extents for async discard

2020-01-20T15:40:58+00:00

The number of discardable extents will serve as the rate limiting metric
for how often we should discard. This keeps track of discardable extents
in the free space caches by maintaining deltas and propagating them to
the global count.

The deltas are calculated from 2 values stored in PREV and CURR entries,
then propagated up to the global discard ctl.  The current counter value
becomes the previous counter value after update.

Signed-off-by: Dennis Zhou 
Reviewed-by: David Sterba 
[ update changelog ]
Signed-off-by: David Sterba

btrfs: sysfs: add UUID/debug/discard directory

2020-01-20T15:40:58+00:00

Setup base sysfs directory for discard stats + tunables.

Reviewed-by: Josef Bacik 
Reviewed-by: Anand Jain 
Signed-off-by: Dennis Zhou 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba