From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Christoph Hellwig <hch@infradead.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
linux-nvdimm@lists.01.org, Linux-MM <linux-mm@kvack.org>,
Linux API <linux-api@vger.kernel.org>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
xfs <linux-xfs@vger.kernel.org>,
"Darrick J . Wong" <darrick.wong@oracle.com>
Subject: Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC
Date: Thu, 12 Apr 2018 15:00:49 +0200 [thread overview]
Message-ID: <CAKgNAkhsFrcdkXNA2cw3o0gJV0uLRtBg9ybaCe5xy1QBC2PgqA@mail.gmail.com> (raw)
In-Reply-To: <20171101153648.30166-20-jack@suse.cz>
Hello Jan,
I have applied your patch, and tweaked the text a little, and pushed
the result to the git repo.
On 1 November 2017 at 16:36, Jan Kara <jack@suse.cz> wrote:
> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
I have a question below.
> ---
> man2/mmap.2 | 35 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 47c3148653be..b38ee6809327 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -125,6 +125,21 @@ are carried through to the underlying file.
> to the underlying file requires the use of
> .BR msync (2).)
> .TP
> +.BR MAP_SHARED_VALIDATE " (since Linux 4.15)"
> +The same as
> +.B MAP_SHARED
> +except that
> +.B MAP_SHARED
> +mappings ignore unknown flags in
> +.IR flags .
> +In contrast when creating mapping of
> +.B MAP_SHARED_VALIDATE
> +mapping type, the kernel verifies all passed flags are known and fails the
> +mapping with
> +.BR EOPNOTSUPP
> +otherwise. This mapping type is also required to be able to use some mapping
> +flags.
> +.TP
> .B MAP_PRIVATE
> Create a private copy-on-write mapping.
> Updates to the mapping are not visible to other processes
> @@ -134,7 +149,10 @@ It is unspecified whether changes made to the file after the
> .BR mmap ()
> call are visible in the mapped region.
> .PP
> -Both of these flags are described in POSIX.1-2001 and POSIX.1-2008.
> +.B MAP_SHARED
> +and
> +.B MAP_PRIVATE
> +are described in POSIX.1-2001 and POSIX.1-2008.
> .PP
> In addition, zero or more of the following values can be ORed in
> .IR flags :
> @@ -352,6 +370,21 @@ option.
> Because of the security implications,
> that option is normally enabled only on embedded devices
> (i.e., devices where one has complete control of the contents of user memory).
> +.TP
> +.BR MAP_SYNC " (since Linux 4.15)"
> +This flags is available only with
> +.B MAP_SHARED_VALIDATE
> +mapping type. Mappings of
> +.B MAP_SHARED
> +type will silently ignore this flag.
> +This flag is supported only for files supporting DAX (direct mapping of persistent
> +memory). For other files, creating mapping with this flag results in
> +.B EOPNOTSUPP
> +error. Shared file mappings with this flag provide the guarantee that while
> +some memory is writeably mapped in the address space of the process, it will
> +be visible in the same file at the same offset even after the system crashes or
> +is rebooted. This allows users of such mappings to make data modifications
> +persistent in a more efficient way using appropriate CPU instructions.
It feels like there's a word missing/unclear wording in the previous
line, before "using". Without that word, the sentence feels a bit
ambiguous.
Should it be:
persistent in a more efficient way *through the use of* appropriate
CPU instructions.
or:
persistent in a more efficient way *than using* appropriate CPU instructions.
?
Is suspect the first is correct, but need to check.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
next prev parent reply other threads:[~2018-04-12 13:01 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-01 15:36 [PATCH 0/18 v6] dax, ext4, xfs: Synchronous page faults Jan Kara
2017-11-01 15:36 ` [PATCH 01/18] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Jan Kara
2017-11-22 12:02 ` Vlastimil Babka
2017-11-22 16:52 ` Dan Williams
2017-11-22 19:53 ` Matthew Wilcox
2017-11-25 18:45 ` Helge Deller
2017-11-27 15:55 ` Vlastimil Babka
2017-11-01 15:36 ` [PATCH 02/18] mm: Remove VM_FAULT_HWPOISON_LARGE_MASK Jan Kara
2017-11-01 15:36 ` [PATCH 03/18] dax: Simplify arguments of dax_insert_mapping() Jan Kara
2017-11-01 15:36 ` [PATCH 04/18] dax: Factor out getting of pfn out of iomap Jan Kara
2017-11-01 15:36 ` [PATCH 05/18] dax: Create local variable for VMA in dax_iomap_pte_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 06/18] dax: Create local variable for vmf->flags & FAULT_FLAG_WRITE test Jan Kara
2017-11-01 15:36 ` [PATCH 07/18] dax: Inline dax_insert_mapping() into the callsite Jan Kara
2017-11-01 15:36 ` [PATCH 08/18] dax: Inline dax_pmd_insert_mapping() " Jan Kara
2017-11-01 15:36 ` [PATCH 09/18] dax: Fix comment describing dax_iomap_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 10/18] dax: Allow dax_iomap_fault() to return pfn Jan Kara
2017-11-01 15:36 ` [PATCH 11/18] dax: Allow tuning whether dax_insert_mapping_entry() dirties entry Jan Kara
2017-11-01 15:36 ` [PATCH 12/18] mm: Define MAP_SYNC and VM_SYNC flags Jan Kara
2017-11-01 15:36 ` [PATCH 13/18] dax, iomap: Add support for synchronous faults Jan Kara
2017-11-01 15:36 ` [PATCH 14/18] dax: Implement dax_finish_sync_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 15/18] ext4: Simplify error handling in ext4_dax_huge_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 16/18] ext4: Support for synchronous DAX faults Jan Kara
2017-11-01 15:36 ` [PATCH 17/18] xfs: Implement xfs_filemap_pfn_mkwrite() using __xfs_filemap_fault() Jan Kara
2017-11-14 2:19 ` Darrick J. Wong
2017-11-01 15:36 ` [PATCH 18/18] xfs: support for synchronous DAX faults Jan Kara
2017-11-14 2:19 ` Darrick J. Wong
2017-11-01 15:36 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Jan Kara
2018-04-12 13:00 ` Michael Kerrisk (man-pages) [this message]
2018-04-12 14:00 ` Ross Zwisler
2018-04-12 14:22 ` Jan Kara
2018-04-12 18:20 ` Michael Kerrisk (man-pages)
2018-04-13 11:17 ` Jan Kara
-- strict thread matches above, loose matches on Subject: below --
2017-10-24 15:23 [PATCH 0/17 v5] dax, ext4, xfs: Synchronous page faults Jan Kara
2017-10-24 15:24 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Jan Kara
2017-10-24 21:10 ` Ross Zwisler
2017-10-26 13:24 ` Jan Kara
2017-10-26 18:22 ` Ross Zwisler
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