linux-kernel - Re: [PATCH] jfs: implement migrate_folio for jfs_metapage

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Message-ID: <255c8ef4-d47a-4559-9c85-c246855347c9@amd.com>
Date: Mon, 14 Apr 2025 10:23:04 +0530
From: Shivank Garg <shivankg@....com>
To: Matthew Wilcox <willy@...radead.org>
Cc: shaggy@...nel.org, jfs-discussion@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org,
 syzbot+8bb6fd945af4e0ad9299@...kaller.appspotmail.com
Subject: Re: [PATCH] jfs: implement migrate_folio for jfs_metapage_aops



On 4/14/2025 2:11 AM, Matthew Wilcox wrote:
> On Sun, Apr 13, 2025 at 05:23:57PM +0000, Shivank Garg wrote:
>> +++ b/fs/jfs/jfs_metapage.c
>> @@ -570,6 +570,7 @@ const struct address_space_operations jfs_metapage_aops = {
>>  	.release_folio	= metapage_release_folio,
>>  	.invalidate_folio = metapage_invalidate_folio,
>>  	.dirty_folio	= filemap_dirty_folio,
>> +	.migrate_folio	= filemap_migrate_folio,
>>  };
> 
> Ooh, damn, I think we're going to need more than this ;-(
> 
> static inline struct metapage *folio_to_mp(struct folio *folio, int offset)
> {
>         return folio->private;
> }
> 
> struct metapage {
> ...
>         void *data;             /* Data pointer */
> 
> So we're going to need something like buffer_migrate_folio(), but
> specialised to jfs metadata.  And when we come up with it, that'll
> be Fixes: 35474d52c605

Thanks for the pointers. I missed the private data aspect earlier.
I think it's doable - IIUC, I'll need to
update mp->folio and mp->data to point to the dst folio info.
I'll work on a patch for it.

Best Regards,
Shivank