On Tue, Dec 05, 2023 at 12:17:31PM +0900, Greg Kroah-Hartman wrote: > 5.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Qu Wenruo <wqu@xxxxxxxx> > > commit 2db313205f8b96eea467691917138d646bb50aef upstream. > > There is a feature request to add dmesg output when unmounting a btrfs. > There are several alternative methods to do the same thing, but with > their own problems: > > - Use eBPF to watch btrfs_put_super()/open_ctree() > Not end user friendly, they have to dip their head into the source > code. > > - Watch for directory /sys/fs/<uuid>/ > This is way more simple, but still requires some simple device -> uuid > lookups. And a script needs to use inotify to watch /sys/fs/. > > Compared to all these, directly outputting the information into dmesg > would be the most simple one, with both device and UUID included. > > And since we're here, also add the output when mounting a filesystem for > the first time for parity. A more fine grained monitoring of subvolume > mounts should be done by another layer, like audit. > > Now mounting a btrfs with all default mkfs options would look like this: > > [81.906566] BTRFS info (device dm-8): first mount of filesystem 633b5c16-afe3-4b79-b195-138fe145e4f2 > [81.907494] BTRFS info (device dm-8): using crc32c (crc32c-intel) checksum algorithm > [81.908258] BTRFS info (device dm-8): using free space tree > [81.912644] BTRFS info (device dm-8): auto enabling async discard > [81.913277] BTRFS info (device dm-8): checking UUID tree > [91.668256] BTRFS info (device dm-8): last unmount of filesystem 633b5c16-afe3-4b79-b195-138fe145e4f2 > > CC: stable@xxxxxxxxxxxxxxx # 5.4+ > Link: https://github.com/kdave/btrfs-progs/issues/689 > Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx> > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > Reviewed-by: David Sterba <dsterba@xxxxxxxx> > [ update changelog ] > Signed-off-by: David Sterba <dsterba@xxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- > fs/btrfs/disk-io.c | 1 + > fs/btrfs/super.c | 5 ++++- > 2 files changed, 5 insertions(+), 1 deletion(-) > > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -2829,6 +2829,7 @@ int open_ctree(struct super_block *sb, > goto fail_alloc; > } > > + btrfs_info(fs_info, "first mount of filesystem %pU", disk_super->fsid); clang tells me this backport does not appear to be correct and will likely introduce a null pointer deference: fs/btrfs/disk-io.c:2832:55: warning: variable 'disk_super' is uninitialized when used here [-Wuninitialized] 2832 | btrfs_info(fs_info, "first mount of filesystem %pU", disk_super->fsid); | ^~~~~~~~~~ fs/btrfs/ctree.h:3002:41: note: expanded from macro 'btrfs_info' 3002 | btrfs_printk(fs_info, KERN_INFO fmt, ##args) | ^~~~ fs/btrfs/disk-io.c:2630:38: note: initialize the variable 'disk_super' to silence this warning 2630 | struct btrfs_super_block *disk_super; | ^ | = NULL 1 warning generated. > /* > * Verify the type first, if that or the checksum value are > * corrupted, we'll find out > --- a/fs/btrfs/super.c > +++ b/fs/btrfs/super.c > @@ -291,7 +291,10 @@ void __btrfs_panic(struct btrfs_fs_info > > static void btrfs_put_super(struct super_block *sb) > { > - close_ctree(btrfs_sb(sb)); > + struct btrfs_fs_info *fs_info = btrfs_sb(sb); > + > + btrfs_info(fs_info, "last unmount of filesystem %pU", fs_info->fs_devices->fsid); > + close_ctree(fs_info); > } > > enum { > >
