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Message-Id: <20171019125817.11580-19-jack@suse.cz> Date: Thu, 19 Oct 2017 14:58:17 +0200 From: Jan Kara <jack@...e.cz> To: <linux-fsdevel@...r.kernel.org> Cc: linux-nvdimm@...ts.01.org, Ross Zwisler <ross.zwisler@...ux.intel.com>, Dan Williams <dan.j.williams@...el.com>, <linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>, Christoph Hellwig <hch@...radead.org>, linux-api@...r.kernel.org, Jan Kara <jack@...e.cz> Subject: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Signed-off-by: Jan Kara <jack@...e.cz> --- man2/mmap.2 | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/man2/mmap.2 b/man2/mmap.2 index 47c3148653be..598ff0c64f7f 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 +.B MAP_SHARED_VALIDATE +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 @@ -352,6 +367,21 @@ 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
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