[PATCH 0/2] btrfs-progs: speed up "btrfs subvolume sync"

[Qu Wenruo <wqu@suse.com>]

Unlike the name, "btrfs subvolume sync" doesn't sync the fs, but only
wait for unlinked subvolumes to be fully deleted.

But that wait completely depends on when the cleaner is woken up, and by
default it takes 30s.

That's why a lot of fstests cases are remount with "commit=1" mount
option to speed "btrfs subvolume sync" up.

To speed things up, and reduce the confusion on the command name, do a
proper BTRFS_IOC_SYNC before waiting for unlinked subvolumes.
That's done in the 2nd patch.

The first patch is minor fix to an uninitilized access, exposed by LLM
during the review of the 2nd patch.

Qu Wenruo (2):
  btrfs-progs: subvolume: fix an uninitialized access
  btrfs-progs: trigger a sync before waiting for subvolumes to be
    dropped

 Documentation/btrfs-subvolume.rst | 7 +++++++
 cmds/subvolume.c                  | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

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2.56.0