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	Thu, 10 Jul 2025 15:16:17 +0000
Date: Thu, 10 Jul 2025 16:16:17 +0100
From: Matthew Wilcox <willy@infradead.org>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: kernel test robot <lkp@intel.com>, llvm@lists.linux.dev,
	oe-kbuild-all@lists.linux.dev,
	linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [jaegeuk-f2fs:dev-test 65/93] fs/f2fs/data.c:58:56: error:
 passing 'const struct folio *' to parameter of type 'struct folio *'
 discards qualifiers
Message-ID: <aG_ZQYONhf9UQJDq@casper.infradead.org>
References: <202507101412.50ND2WEX-lkp@intel.com>
 <aG_Gr8NvCiXC4SyU@casper.infradead.org>
 <aG_NntbzliX0WUGB@google.com>
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In-Reply-To: <aG_NntbzliX0WUGB@google.com>

On Thu, Jul 10, 2025 at 02:26:38PM +0000, Jaegeuk Kim wrote:
> On 07/10, Matthew Wilcox wrote:
> > On Thu, Jul 10, 2025 at 03:17:28PM +0800, kernel test robot wrote:
> > > >> fs/f2fs/data.c:58:56: error: passing 'const struct folio *' to parameter of type 'struct folio *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
> > >       58 |                 return folio_test_f2fs_gcing(fscrypt_pagecache_folio(folio));
> > >          |                                                                      ^~~~~
> > >    include/linux/fscrypt.h:527:67: note: passing argument to parameter 'bounce_folio' here
> > >      527 | static inline struct folio *fscrypt_pagecache_folio(struct folio *bounce_folio)
> > 
> > Ah; I changed only one of the definitions of fscrypt_pagecache_folio.
> > 
> > Jaegeuk, can you fold in this fix?
> 
> Will this break ext4?
> 
> In ext4,
> 		struct folio *folio = fi.folio;
> 		...
> 
> 		if (fscrypt_is_bounce_folio(folio)) {
> 			io_folio = folio;
> 			folio = fscrypt_pagecache_folio(folio);
> 		}

No, you can pass a mutable folio to a function which takes a const
folio.  Just not the other way around.