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From: "Theodore Ts'o" <tytso@mit.edu>
To: Matthew Wilcox <willy@infradead.org>
Cc: Lee Jones <lee.jones@linaro.org>,
	linux-ext4@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Dave Chinner <dchinner@redhat.com>,
	Goldwyn Rodrigues <rgoldwyn@suse.com>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	Bob Peterson <rpeterso@redhat.com>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Ritesh Harjani <riteshh@linux.ibm.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Johannes Thumshirn <jth@kernel.org>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	cluster-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers()
Date: Fri, 18 Feb 2022 01:03:13 -0500	[thread overview]
Message-ID: <Yg82oSHmodFHMHHI@mit.edu> (raw)
In-Reply-To: <Yg8fdCuE6RusrjIh@casper.infradead.org>

On Fri, Feb 18, 2022 at 04:24:20AM +0000, Matthew Wilcox wrote:
> On Thu, Feb 17, 2022 at 09:54:30PM -0500, Theodore Ts'o wrote:
> > process_vm_writev() uses [un]pin_user_pages_remote() which is the same
> > interface uses for RDMA.  But it's not clear this is ever supposed to
> > work for memory which is mmap'ed region backed by a file.
> > pin_user_pages_remote() appears to assume that it is an anonymous
> > region, since the get_user_pages functions in mm/gup.c don't call
> > read_page() to read data into any pages that might not be mmaped in.
> 
> ... it doesn't end up calling handle_mm_fault() in faultin_page()?

Ah yes, sorry, I missed that.  This is what happens when a syzbot bug
is thrown to a file system developer, who then has to wade theough
mm code for which he is not understand....

	   	    	     	    - Ted
			    

WARNING: multiple messages have this Message-ID (diff)
From: Theodore Ts'o <tytso@mit.edu>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers()
Date: Fri, 18 Feb 2022 01:03:13 -0500	[thread overview]
Message-ID: <Yg82oSHmodFHMHHI@mit.edu> (raw)
In-Reply-To: <Yg8fdCuE6RusrjIh@casper.infradead.org>

On Fri, Feb 18, 2022 at 04:24:20AM +0000, Matthew Wilcox wrote:
> On Thu, Feb 17, 2022 at 09:54:30PM -0500, Theodore Ts'o wrote:
> > process_vm_writev() uses [un]pin_user_pages_remote() which is the same
> > interface uses for RDMA.  But it's not clear this is ever supposed to
> > work for memory which is mmap'ed region backed by a file.
> > pin_user_pages_remote() appears to assume that it is an anonymous
> > region, since the get_user_pages functions in mm/gup.c don't call
> > read_page() to read data into any pages that might not be mmaped in.
> 
> ... it doesn't end up calling handle_mm_fault() in faultin_page()?

Ah yes, sorry, I missed that.  This is what happens when a syzbot bug
is thrown to a file system developer, who then has to wade theough
mm code for which he is not understand....

	   	    	     	    - Ted
			    



  reply	other threads:[~2022-02-18  6:03 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-16 16:31 [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers() Lee Jones
2022-02-16 16:31 ` [Cluster-devel] " Lee Jones
2022-02-18  1:06 ` John Hubbard
2022-02-18  1:06   ` [Cluster-devel] " John Hubbard
2022-02-18  4:08   ` Theodore Ts'o
2022-02-18  4:08     ` [Cluster-devel] " Theodore Ts'o
2022-02-18  6:33     ` John Hubbard
2022-02-18  6:33       ` [Cluster-devel] " John Hubbard
2022-02-23 23:31       ` Theodore Ts'o
2022-02-23 23:31         ` [Cluster-devel] " Theodore Ts'o
2022-02-24  0:44         ` John Hubbard
2022-02-24  0:44           ` [Cluster-devel] " John Hubbard
2022-02-24  4:04           ` Theodore Ts'o
2022-02-24  4:04             ` [Cluster-devel] " Theodore Ts'o
2022-02-18  7:51     ` Greg Kroah-Hartman
2022-02-18  7:51       ` [Cluster-devel] " Greg Kroah-Hartman
2022-02-23 23:35       ` Theodore Ts'o
2022-02-23 23:35         ` [Cluster-devel] " Theodore Ts'o
2022-02-24  1:48         ` Dave Chinner
2022-02-24  1:48           ` [Cluster-devel] " Dave Chinner
2022-02-24  3:50           ` Theodore Ts'o
2022-02-24  3:50             ` [Cluster-devel] " Theodore Ts'o
2022-02-24 10:29             ` Dave Chinner
2022-02-24 10:29               ` [Cluster-devel] " Dave Chinner
2022-02-18  2:54 ` Theodore Ts'o
2022-02-18  2:54   ` [Cluster-devel] " Theodore Ts'o
2022-02-18  4:24   ` Matthew Wilcox
2022-02-18  4:24     ` [Cluster-devel] " Matthew Wilcox
2022-02-18  6:03     ` Theodore Ts'o [this message]
2022-02-18  6:03       ` Theodore Ts'o
2022-02-25 19:24 ` [PATCH -v2] ext4: don't BUG if kernel subsystems dirty pages without asking ext4 first Theodore Ts'o
2022-02-25 19:24   ` [Cluster-devel] " Theodore Ts'o
2022-02-25 20:51   ` Eric Biggers
2022-02-25 20:51     ` [Cluster-devel] " Eric Biggers
2022-02-25 21:08     ` Theodore Ts'o
2022-02-25 21:08       ` [Cluster-devel] " Theodore Ts'o
2022-02-25 21:23       ` [PATCH -v3] " Theodore Ts'o
2022-02-25 21:23         ` [Cluster-devel] " Theodore Ts'o
2022-02-25 21:33         ` John Hubbard
2022-02-25 21:33           ` [Cluster-devel] " John Hubbard
2022-02-25 23:21           ` Theodore Ts'o
2022-02-25 23:21             ` [Cluster-devel] " Theodore Ts'o
2022-02-26  0:18             ` Hillf Danton
2022-02-26  0:41             ` John Hubbard
2022-02-26  0:41               ` [Cluster-devel] " John Hubbard
2022-02-26  1:40               ` Theodore Ts'o
2022-02-26  1:40                 ` [Cluster-devel] " Theodore Ts'o
2022-02-26  2:00                 ` Theodore Ts'o
2022-02-26  2:00                   ` [Cluster-devel] " Theodore Ts'o
2022-02-26  2:55                 ` John Hubbard
2022-02-26  2:55                   ` [Cluster-devel] " John Hubbard
2022-03-03  4:26         ` [PATCH -v4] " Theodore Ts'o
2022-03-03  4:26           ` [Cluster-devel] " Theodore Ts'o
2022-03-03  8:21           ` Christoph Hellwig
2022-03-03  8:21             ` [Cluster-devel] " Christoph Hellwig
2022-03-03  9:21           ` Lee Jones
2022-03-03  9:21             ` [Cluster-devel] " Lee Jones
2022-03-03 14:38           ` [PATCH -v5] ext4: don't BUG if someone " Theodore Ts'o
2022-03-03 14:38             ` [Cluster-devel] " Theodore Ts'o

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