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From: Matthew Wilcox <willy@infradead.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
	Miklos Szeredi <miklos@szeredi.hu>,
	kbuild test robot <lkp@intel.com>,
	kbuild-all@lists.01.org, Colin Walters <walters@verbum.org>,
	syzbot <syzbot+d6ec23007e951dadf3de@syzkaller.appspotmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area()
Date: Wed, 10 Jun 2020 18:36:16 -0700	[thread overview]
Message-ID: <20200611013616.GM19604@bombadil.infradead.org> (raw)
In-Reply-To: <20200611003726.GY23230@ZenIV.linux.org.uk>

On Thu, Jun 11, 2020 at 01:37:26AM +0100, Al Viro wrote:
> On Wed, Jun 10, 2020 at 05:13:52PM -0700, Mike Kravetz wrote:
> 
> > To address this issue,
> > - Add a new file operation f_real while will return the underlying file.
> >   Only overlayfs provides a function for this operation.
> > - Add a new routine real_file() which can be used by core code get an
> >   underlying file.
> > - Update is_file_hugepages to get the real file.
> 
> Egads...  So to find out whether it's a hugetlb you would
> 	* check if a method is NULL
> 	* if not, call it
> 	* ... and check if the method table of the result is hugetlbfs one?
> 
> Here's a radical suggestion: FMODE_HUGEPAGES.  Just have it set by
> ->open() and let is_file_hugepages() check it.  In ->f_mode.  And
> make the bloody hugetlbfs_file_operations static, while we are at it.

ITYM FMODE_OVL_UPPER.  To quote Mike:

>         while (file->f_op == &ovl_file_operations)
>                 file = file->private_data;
>         return file;

which would be transformed into:

	while (file->f_mode & FMODE_OVL_UPPER)
		file = file->private_data;
	return file;

Or are you proposing that overlayfs copy FMODE_HUGEPAGES from the
underlying fs to the overlaying fs?

WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <willy@infradead.org>
To: kbuild-all@lists.01.org
Subject: Re: [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area()
Date: Wed, 10 Jun 2020 18:36:16 -0700	[thread overview]
Message-ID: <20200611013616.GM19604@bombadil.infradead.org> (raw)
In-Reply-To: <20200611003726.GY23230@ZenIV.linux.org.uk>

[-- Attachment #1: Type: text/plain, Size: 1250 bytes --]

On Thu, Jun 11, 2020 at 01:37:26AM +0100, Al Viro wrote:
> On Wed, Jun 10, 2020 at 05:13:52PM -0700, Mike Kravetz wrote:
> 
> > To address this issue,
> > - Add a new file operation f_real while will return the underlying file.
> >   Only overlayfs provides a function for this operation.
> > - Add a new routine real_file() which can be used by core code get an
> >   underlying file.
> > - Update is_file_hugepages to get the real file.
> 
> Egads...  So to find out whether it's a hugetlb you would
> 	* check if a method is NULL
> 	* if not, call it
> 	* ... and check if the method table of the result is hugetlbfs one?
> 
> Here's a radical suggestion: FMODE_HUGEPAGES.  Just have it set by
> ->open() and let is_file_hugepages() check it.  In ->f_mode.  And
> make the bloody hugetlbfs_file_operations static, while we are at it.

ITYM FMODE_OVL_UPPER.  To quote Mike:

>         while (file->f_op == &ovl_file_operations)
>                 file = file->private_data;
>         return file;

which would be transformed into:

	while (file->f_mode & FMODE_OVL_UPPER)
		file = file->private_data;
	return file;

Or are you proposing that overlayfs copy FMODE_HUGEPAGES from the
underlying fs to the overlaying fs?

  reply	other threads:[~2020-06-11  1:36 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-06  3:06 kernel BUG at mm/hugetlb.c:LINE! syzbot
2020-04-06  3:06 ` syzbot
2020-04-06 22:05 ` Mike Kravetz
2020-05-12 15:04   ` Miklos Szeredi
2020-05-12 15:04     ` Miklos Szeredi
2020-05-12 18:11     ` Mike Kravetz
2020-05-15 22:15       ` Mike Kravetz
2020-05-18 11:12         ` Miklos Szeredi
2020-05-18 11:12           ` Miklos Szeredi
2020-05-18 23:22           ` Mike Kravetz
2020-05-18 23:41     ` Colin Walters
2020-05-19  0:35       ` Mike Kravetz
2020-05-20 11:20         ` Miklos Szeredi
2020-05-20 11:20           ` Miklos Szeredi
2020-05-20 17:27           ` Mike Kravetz
2020-05-22 10:05             ` Miklos Szeredi
2020-05-28  0:01               ` Mike Kravetz
2020-05-28  8:37                 ` [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area() kbuild test robot
2020-05-28  8:37                   ` kbuild test robot
2020-05-28 21:01                   ` Mike Kravetz
2020-05-28 21:01                     ` Mike Kravetz
2020-06-04  9:16                     ` Miklos Szeredi
2020-06-04  9:16                       ` Miklos Szeredi
2020-06-04  9:16                       ` Miklos Szeredi
2020-06-11  0:13                       ` Mike Kravetz
2020-06-11  0:13                         ` Mike Kravetz
2020-06-11  0:37                         ` Al Viro
2020-06-11  0:37                           ` Al Viro
2020-06-11  1:36                           ` Matthew Wilcox [this message]
2020-06-11  1:36                             ` Matthew Wilcox
2020-06-11  2:17                             ` Al Viro
2020-06-11  2:17                               ` Al Viro
2020-06-11  2:31                               ` Mike Kravetz
2020-06-11  2:31                                 ` Mike Kravetz

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