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Date:   Thu, 8 Dec 2022 17:54:52 -0500
From:   Eric Whitney <enwlinux@...il.com>
To:     Eric Whitney <enwlinux@...il.com>
Cc:     Ye Bin <yebin@...weicloud.com>, tytso@....edu,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, jack@...e.cz,
        Ye Bin <yebin10@...wei.com>,
        syzbot+05a0f0ccab4a25626e38@...kaller.appspotmail.com
Subject: Re: [PATCH v3 1/3] ext4: fix incorrect calculate 'reserved' in
 '__es_remove_extent' when enable bigalloc feature

* Eric Whitney <enwlinux@...il.com>:
> * Eric Whitney <enwlinux@...il.com>:
> > * Ye Bin <yebin@...weicloud.com>:
> > > From: Ye Bin <yebin10@...wei.com>
> > > 
> > > Syzbot report issue as follows:
> > > EXT4-fs error (device loop0): ext4_validate_block_bitmap:398: comm rep: bg 0: block 5: invalid block bitmap
> > > EXT4-fs (loop0): Delayed block allocation failed for inode 18 at logical offset 0 with max blocks 32 with error 28
> > > EXT4-fs (loop0): This should not happen!! Data will be lost
> > > 
> > > EXT4-fs (loop0): Total free blocks count 0
> > > EXT4-fs (loop0): Free/Dirty block details
> > > EXT4-fs (loop0): free_blocks=0
> > > EXT4-fs (loop0): dirty_blocks=32
> > > EXT4-fs (loop0): Block reservation details
> > > EXT4-fs (loop0): i_reserved_data_blocks=2
> > > EXT4-fs (loop0): Inode 18 (00000000845cd634): i_reserved_data_blocks (1) not cleared!
> > > 
> > > Above issue happens as follows:
> > > Assume:
> > > sbi->s_cluster_ratio = 16
> > > Step1: Insert delay block [0, 31] -> ei->i_reserved_data_blocks=2
> > > Step2:
> > > ext4_writepages
> > >   mpage_map_and_submit_extent -> return failed
> > >   mpage_release_unused_pages -> to release [0, 30]
> > >     ext4_es_remove_extent -> remove lblk=0 end=30
> > >       __es_remove_extent -> len1=0 len2=31-30=1
> > >  __es_remove_extent:
> > >  ...
> > >  if (len2 > 0) {
> > >   ...
> > > 	  if (len1 > 0) {
> > > 		  ...
> > > 	  } else {
> > > 		es->es_lblk = end + 1;
> > > 		es->es_len = len2;
> > > 		...
> > > 	  }
> > >   	if (count_reserved)
> > > 		count_rsvd(inode, lblk, orig_es.es_len - len1 - len2, &orig_es, &rc);
> > > 	goto out; -> will return but didn't calculate 'reserved'
> > >  ...
> > > Step3: ext4_destroy_inode -> trigger "i_reserved_data_blocks (1) not cleared!"
> > > 
> > > To solve above issue if 'len2>0' call 'get_rsvd()' before goto out.
> > > 
> > > Reported-by: syzbot+05a0f0ccab4a25626e38@...kaller.appspotmail.com
> > > Fixes: 8fcc3a580651 ("ext4: rework reserved cluster accounting when invalidating pages")
> > > Signed-off-by: Ye Bin <yebin10@...wei.com>
> > > ---
> > >  fs/ext4/extents_status.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> > > index cd0a861853e3..7ada374ff27d 100644
> > > --- a/fs/ext4/extents_status.c
> > > +++ b/fs/ext4/extents_status.c
> > > @@ -1371,7 +1371,7 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> > >  		if (count_reserved)
> > >  			count_rsvd(inode, lblk, orig_es.es_len - len1 - len2,
> > >  				   &orig_es, &rc);
> > > -		goto out;
> > > +		goto out_get_reserved;
> > >  	}
> > >  
> > >  	if (len1 > 0) {
> > > @@ -1413,6 +1413,7 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> > >  		}
> > >  	}
> > >  
> > > +out_get_reserved:
> > >  	if (count_reserved)
> > >  		*reserved = get_rsvd(inode, end, es, &rc);
> > >  out:
> > 
> > The length of some lines in the commit description - probably those which are
> > log output - is resulting in a checkpatch warning.  It generally prefers lines
> > to be a maximum of 75 characters (and Ted usually likes them limited to 72
> > characters.  See my comment to patch #3. I'm not sure what Ted would want here,
> > though I'd probably break them at 72 characters or less.
> > 
> > Otherwise, the patch looks good.  Feel free to add:
> > 
> 
> Looks good.  As before, feel free to add:
> 
> > Reviewed-by: Eric Whitney <enwlinux@...il.com>
> 

Whoops.  Please disregard - wrong patch.

Eric

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