linux-kernel - Re: [PATCH v3] bcachefs: init freespace inited bits to 0 in bch2_fs

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Message-ID: <ZE-D4gWuaHm-NpPnk8yUxXY4ouYy492LCPmnEgWG3fiIleDRGZU9SjbSbYiVWPa2_OYirT-Jx_E7b5NsSh9s6Txvnkc0KRsGHNKHH1umkDE=@proton.me>
Date: Sat, 26 Oct 2024 13:40:47 +0000
From: Piotr Zalewski <pZ010001011111@...ton.me>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, skhan@...uxfoundation.org, syzbot+2b6a17991a6af64f9489@...kaller.appspotmail.com
Subject: Re: [PATCH v3] bcachefs: init freespace inited bits to 0 in bch2_fs_initialize

On Saturday, October 26th, 2024 at 2:30 AM, Kent Overstreet <kent.overstreet@...ux.dev> wrote:

> On Sat, Oct 26, 2024 at 12:15:49AM +0000, Piotr Zalewski wrote:
> 
> > Initialize freespace_initialized bits to 0 in member's flags and update
> > member's cached version for each device in bch2_fs_initialize.
> > 
> > It's possible for the bits to be set to 1 before fs is initialized and if
> > call to bch2_trans_mark_dev_sbs (just before bch2_fs_freespace_init) fails
> > bits remain to be 1 which can later indirectly trigger BUG condition in
> > bch2_bucket_alloc_freelist during shutdown.
> > 
> > Reported-by: syzbot+2b6a17991a6af64f9489@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
> > Fixes: bbe682c76789 ("bcachefs: Ensure devices are always correctly initialized")
> > Suggested-by: Kent Overstreet kent.overstreet@...ux.dev
> > Signed-off-by: Piotr Zalewski pZ010001011111@...ton.me
> > ---
> > 
> > Notes:
> > changes in v3:
> > - v2 rebased
> > 
> > changes in v2:
> > - unconditionally set freespace initialized bits to false at
> > the top of bch2_fs_initialized instead of only if
> > bch2_trans_mark_dev_sbs fails
> > 
> > Link to v2: https://lore.kernel.org/linux-bcachefs/20241021174151.37692-2-pZ010001011111@proton.me/
> > Link to v1: https://lore.kernel.org/linux-bcachefs/20241020170708.67044-2-pZ010001011111@proton.me/
> > 
> > fs/bcachefs/recovery.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> > 
> > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
> > index fdf2aa2ffc13..8d4c93a1f5aa 100644
> > --- a/fs/bcachefs/recovery.c
> > +++ b/fs/bcachefs/recovery.c
> > @@ -1029,6 +1029,7 @@ int bch2_fs_initialize(struct bch_fs *c)
> > struct bch_inode_unpacked root_inode, lostfound_inode;
> > struct bkey_inode_buf packed_inode;
> > struct qstr lostfound = QSTR("lost+found");
> > + struct bch_member *m;
> > int ret;
> > 
> > bch_notice(c, "initializing new filesystem");
> > @@ -1045,6 +1046,13 @@ int bch2_fs_initialize(struct bch_fs *c)
> > SET_BCH_SB_VERSION_UPGRADE_COMPLETE(c->disk_sb.sb, bcachefs_metadata_version_current);
> > bch2_write_super(c);
> > }
> > +
> > + for_each_member_device(c, ca) {
> > + m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
> > + SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, false);
> > + ca->mi = bch2_mi_to_cpu(m);
> > + }
> > +
> 
> 
> I'm also adding a write_super() call here: that's what updates
> ca->mi.freespace_initialized which the freespace init path will later
> 
> check.

Do you want me to send v4? Or you will add it with separate patch?

Best regards, Piotr Zalewski

> > mutex_unlock(&c->sb_lock);
> > 
> > c->curr_recovery_pass = BCH_RECOVERY_PASS_NR;
> > --
> > 2.47.0