linux-kernel - [PATCH 5/5] btrfs: ioctl: Call btrfs_vol

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Date:   Wed, 23 Oct 2019 23:36:36 -0300
From:   Marcos Paulo de Souza <marcos.souza.org@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     clm@...com, josef@...icpanda.com, dsterba@...e.com,
        linux-btrfs@...r.kernel.org, mpdesouza@...e.com
Subject: [PATCH 5/5] btrfs: ioctl: Call btrfs_vol_uevent on subvolume deletion

From: Marcos Paulo de Souza <mpdesouza@...e.com>

Since the function btrfs_ioctl_snap_destroy is used for deleting both
subvolumes and snapshots it was needed call btrfs_is_snapshot,
which checks a giver btrfs_root and returns true if it's a snapshot.
The current code is interested in subvolumes only.

btrfs_vol_uevent will export two environment variables to udev:
BTRFS_VOL_NAME: containing the name of the subvolume deleted
BTRFS_VOL_DEL: will signalize that a volume is being deleted

One can create a udev rule and check for BTRFS_VOL_DEL being set,
these values one could detect whenever a subvolume is deleted, and
take any action based on the subvolume name contained in BTRFS_VOL_NAME.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@...e.com>
---
 fs/btrfs/ioctl.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index c538d3648195..173f2a258508 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2869,6 +2869,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 {
 	struct dentry *parent = file->f_path.dentry;
 	struct btrfs_fs_info *fs_info = btrfs_sb(parent->d_sb);
+	struct block_device *bdev = fs_info->fs_devices->latest_bdev;
 	struct dentry *dentry;
 	struct inode *dir = d_inode(parent);
 	struct inode *inode;
@@ -2962,6 +2963,10 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 	err = btrfs_delete_subvolume(dir, dentry);
 	inode_unlock(inode);
 	if (!err) {
+		/* send uevent only to subvolume deletion */
+		if (!btrfs_is_snapshot(dest))
+			btrfs_vol_uevent(bdev, false, vol_args->name);
+
 		fsnotify_rmdir(dir, dentry);
 		d_delete(dentry);
 	}
-- 
2.23.0