From: Jan Kara <jack@suse.cz>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jan Kara <jack@suse.cz>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Dave Chinner <dchinner@redhat.com>, Jann Horn <jannh@google.com>,
Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>,
Kirill Shutemov <kirill@shutemov.name>,
Theodore Ts'o <tytso@mit.edu>,
Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH 1/2] ext2: don't update mtime on COW faults
Date: Mon, 7 Sep 2020 11:00:37 +0200 [thread overview]
Message-ID: <20200907090037.GB16559@quack2.suse.cz> (raw)
In-Reply-To: <alpine.LRH.2.02.2009050811200.12419@file01.intranet.prod.int.rdu2.redhat.com>
On Sat 05-09-20 08:12:01, Mikulas Patocka wrote:
> When running in a dax mode, if the user maps a page with MAP_PRIVATE and
> PROT_WRITE, the ext2 filesystem would incorrectly update ctime and mtime
> when the user hits a COW fault.
>
> This breaks building of the Linux kernel.
> How to reproduce:
> 1. extract the Linux kernel tree on dax-mounted ext2 filesystem
> 2. run make clean
> 3. run make -j12
> 4. run make -j12
> - at step 4, make would incorrectly rebuild the whole kernel (although it
> was already built in step 3).
>
> The reason for the breakage is that almost all object files depend on
> objtool. When we run objtool, it takes COW page fault on its .data
> section, and these faults will incorrectly update the timestamp of the
> objtool binary. The updated timestamp causes make to rebuild the whole
> tree.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
Thanks. Good spotting! Linus has already merged this so nothing more to do
here.
Honza
>
> ---
> fs/ext2/file.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/fs/ext2/file.c
> ===================================================================
> --- linux-2.6.orig/fs/ext2/file.c 2020-09-05 10:01:41.000000000 +0200
> +++ linux-2.6/fs/ext2/file.c 2020-09-05 13:09:50.000000000 +0200
> @@ -93,8 +93,10 @@ static vm_fault_t ext2_dax_fault(struct
> struct inode *inode = file_inode(vmf->vma->vm_file);
> struct ext2_inode_info *ei = EXT2_I(inode);
> vm_fault_t ret;
> + bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
> + (vmf->vma->vm_flags & VM_SHARED);
>
> - if (vmf->flags & FAULT_FLAG_WRITE) {
> + if (write) {
> sb_start_pagefault(inode->i_sb);
> file_update_time(vmf->vma->vm_file);
> }
> @@ -103,7 +105,7 @@ static vm_fault_t ext2_dax_fault(struct
> ret = dax_iomap_fault(vmf, PE_SIZE_PTE, NULL, NULL, &ext2_iomap_ops);
>
> up_read(&ei->dax_sem);
> - if (vmf->flags & FAULT_FLAG_WRITE)
> + if (write)
> sb_end_pagefault(inode->i_sb);
> return ret;
> }
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
next prev parent reply other threads:[~2020-09-07 9:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 19:24 a crash when running strace from persistent memory Mikulas Patocka
2020-09-03 19:55 ` Linus Torvalds
2020-09-04 8:08 ` Mikulas Patocka
2020-09-04 17:11 ` Linus Torvalds
2020-09-04 16:21 ` make misbehavior on ext2 in dax mode (was: a crash when running strace from persistent memory) Mikulas Patocka
2020-09-05 12:11 ` Mikulas Patocka
2020-09-05 12:12 ` [PATCH 1/2] ext2: don't update mtime on COW faults Mikulas Patocka
2020-09-07 9:00 ` Jan Kara [this message]
2020-09-05 12:13 ` [PATCH 2/2] xfs: " Mikulas Patocka
2020-09-05 15:36 ` Darrick J. Wong
2020-09-05 17:02 ` Mikulas Patocka
2020-09-10 6:06 ` Darrick J. Wong
2020-09-11 16:41 ` Mikulas Patocka
2020-09-05 16:47 ` Linus Torvalds
2020-09-05 17:03 ` Linus Torvalds
2020-09-07 8:59 ` Jan Kara
2020-09-05 17:04 ` [PATCH 2/2 v2] " Mikulas Patocka
2020-09-07 6:47 ` [PATCH 2/2] " Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200907090037.GB16559@quack2.suse.cz \
--to=jack@suse.cz \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=darrick.wong@oracle.com \
--cc=dchinner@redhat.com \
--cc=hch@lst.de \
--cc=jannh@google.com \
--cc=kirill@shutemov.name \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nvdimm@lists.01.org \
--cc=linux-xfs@vger.kernel.org \
--cc=mpatocka@redhat.com \
--cc=oleg@redhat.com \
--cc=torvalds@linux-foundation.org \
--cc=tytso@mit.edu \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).