From: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"Darrick J . Wong"
<darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC
Date: Wed, 1 Nov 2017 16:36:48 +0100 [thread overview]
Message-ID: <20171101153648.30166-20-jack@suse.cz> (raw)
In-Reply-To: <20171101153648.30166-1-jack-AlSwsSmVLrQ@public.gmane.org>
Reviewed-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Signed-off-by: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
---
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.
.PP
Of the above flags, only
.B MAP_FIXED
--
2.12.3
next prev parent reply other threads:[~2017-11-01 15:36 UTC|newest]
Thread overview: 40+ 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 02/18] mm: Remove VM_FAULT_HWPOISON_LARGE_MASK Jan Kara
2017-11-01 15:36 ` [PATCH 04/18] dax: Factor out getting of pfn out of iomap Jan Kara
[not found] ` <20171101153648.30166-1-jack-AlSwsSmVLrQ@public.gmane.org>
2017-11-01 15:36 ` [PATCH 01/18] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Jan Kara
[not found] ` <20171101153648.30166-2-jack-AlSwsSmVLrQ@public.gmane.org>
2017-11-22 12:02 ` Vlastimil Babka
2017-11-22 16:52 ` Dan Williams
[not found] ` <CAPcyv4gGRHWc6AH5Enb7njtmqHgd=g+0-mYMdd5wWjJMW0+d7g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
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 03/18] dax: Simplify arguments of dax_insert_mapping() 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 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
[not found] ` <20171101153648.30166-18-jack-AlSwsSmVLrQ@public.gmane.org>
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 ` Jan Kara [this message]
[not found] ` <20171101153648.30166-20-jack-AlSwsSmVLrQ@public.gmane.org>
2018-04-12 13:00 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Michael Kerrisk (man-pages)
[not found] ` <CAKgNAkhsFrcdkXNA2cw3o0gJV0uLRtBg9ybaCe5xy1QBC2PgqA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-12 14:00 ` Ross Zwisler
2018-04-12 14:22 ` Jan Kara
[not found] ` <20180412142214.fcxw3g2jxv6bvn7d-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2018-04-12 18:20 ` Michael Kerrisk (man-pages)
[not found] ` <CAKgNAkgtVryFb81QgzwPq8SD241yKDN1xNxOWUUQH9QBYV13SA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-13 11:17 ` Jan Kara
2017-11-01 15:36 ` [PATCH 08/18] dax: Inline dax_pmd_insert_mapping() into the callsite 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
[not found] ` <20171024152415.22864-1-jack-AlSwsSmVLrQ@public.gmane.org>
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
[not found] ` <20171026132402.GB31161-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2017-10-26 18:22 ` Ross Zwisler
2017-10-19 12:57 [PATCH 0/17 v4] dax, ext4, xfs: Synchronous page faults Jan Kara
[not found] ` <20171019125817.11580-1-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-19 12:58 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Jan Kara
[not found] ` <20171019125817.11580-19-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-20 21:47 ` Ross Zwisler
[not found] ` <20171020214753.GA15733-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-10-24 13:27 ` Jan Kara
[not found] ` <20171024132713.GD8556-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2017-10-24 14:55 ` Ross Zwisler
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