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Date:   Thu, 8 Dec 2022 17:53:24 -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>:
> * 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>

> 
> > -- 
> > 2.31.1
> > 

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