From: Jan Kara <jack@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>
Cc: linux-nvdimm@lists.01.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, jthumshirn@suse.de
Subject: Problems with VM_MIXEDMAP removal from /proc/<pid>/smaps
Date: Tue, 2 Oct 2018 12:05:31 +0200 [thread overview]
Message-ID: <20181002100531.GC4135@quack2.suse.cz> (raw)
[-- Attachment #1: Type: text/plain, Size: 951 bytes --]
Hello,
commit e1fb4a086495 "dax: remove VM_MIXEDMAP for fsdax and device dax" has
removed VM_MIXEDMAP flag from DAX VMAs. Now our testing shows that in the
mean time certain customer of ours started poking into /proc/<pid>/smaps
and looks at VMA flags there and if VM_MIXEDMAP is missing among the VMA
flags, the application just fails to start complaining that DAX support is
missing in the kernel. The question now is how do we go about this?
Strictly speaking, this is a userspace visible regression (as much as I
think that application poking into VMA flags at this level is just too
bold). Is there any precedens in handling similar issues with smaps which
really exposes a lot of information that is dependent on kernel
implementation details?
I have attached a patch that is an obvious "fix" for the issue - just fake
VM_MIXEDMAP flag in smaps. But I'm open to other suggestions...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
[-- Attachment #2: 0001-proc-Show-DAX-mappings-as-having-VM_MIXEDMAP-flag.patch --]
[-- Type: text/x-patch, Size: 0 bytes --]
next reply other threads:[~2018-10-02 10:05 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 10:05 Jan Kara [this message]
2018-10-02 10:50 ` Problems with VM_MIXEDMAP removal from /proc/<pid>/smaps Michal Hocko
2018-10-02 13:32 ` Jan Kara
2018-10-02 12:10 ` Johannes Thumshirn
2018-10-02 14:20 ` Johannes Thumshirn
2018-10-02 14:45 ` Christoph Hellwig
2018-10-02 15:01 ` Johannes Thumshirn
2018-10-02 15:06 ` Christoph Hellwig
2018-10-04 10:09 ` Johannes Thumshirn
2018-10-05 6:25 ` Christoph Hellwig
2018-10-05 6:35 ` Johannes Thumshirn
2018-10-06 1:17 ` Dan Williams
2018-10-14 15:47 ` Dan Williams
2018-10-17 20:01 ` Dan Williams
2018-10-18 17:43 ` Jan Kara
2018-10-18 19:10 ` Dan Williams
2018-10-19 3:01 ` Dave Chinner
2018-10-02 14:29 ` Jan Kara
2018-10-02 14:37 ` Christoph Hellwig
2018-10-02 14:44 ` Johannes Thumshirn
2018-10-02 14:52 ` Christoph Hellwig
2018-10-02 15:31 ` Jan Kara
2018-10-02 20:18 ` Dan Williams
2018-10-03 12:50 ` Jan Kara
2018-10-03 14:38 ` Dan Williams
2018-10-03 15:06 ` Jan Kara
2018-10-03 15:13 ` Dan Williams
2018-10-03 16:44 ` Jan Kara
2018-10-03 21:13 ` Dan Williams
2018-10-04 10:04 ` Johannes Thumshirn
2018-10-02 15:07 ` Jan Kara
2018-10-17 20:23 ` Jeff Moyer
2018-10-18 0:25 ` Dave Chinner
2018-10-18 14:55 ` Jan Kara
2018-10-19 0:43 ` Dave Chinner
2018-10-30 6:30 ` Dan Williams
2018-10-30 22:49 ` Dave Chinner
2018-10-30 22:59 ` Dan Williams
2018-10-31 5:59 ` y-goto
2018-11-01 23:00 ` Dave Chinner
2018-11-02 1:43 ` y-goto
2018-10-18 21:05 ` Jeff Moyer
2018-10-09 19:43 ` Jeff Moyer
2018-10-16 8:25 ` Jan Kara
2018-10-16 12:35 ` Jeff Moyer
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