Hello Ira, On 9/28/20 6:42 PM, Ira Weiny wrote: > On Mon, May 04, 2020 at 05:20:16PM -0700, 'Ira Weiny' wrote: >> From: Ira Weiny <ira.weiny@xxxxxxxxx> >> >> Linux 5.8 is slated to have STATX_ATTR_DAX support. >> >> https://lore.kernel.org/lkml/20200428002142.404144-4-ira.weiny@xxxxxxxxx/ >> https://lore.kernel.org/lkml/20200504161352.GA13783@magnolia/ >> >> Add the text to the statx man page. >> >> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > Have I sent this to the wrong list? Or perhaps I have missed a reply. No, it's just me being a bit slow, I'm sorry. Thank you for pining. > I don't see this applied to the man-pages project.[1] But perhaps I am looking > at the wrong place? Your patch is applied now, and pushed to kernel .org. Thanks! Cheers, Michael > [1] git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git > >> --- >> man2/statx.2 | 24 ++++++++++++++++++++++++ >> 1 file changed, 24 insertions(+) >> >> diff --git a/man2/statx.2 b/man2/statx.2 >> index 2e90f07dbdbc..14c4ab78e7bd 100644 >> --- a/man2/statx.2 >> +++ b/man2/statx.2 >> @@ -468,6 +468,30 @@ The file has fs-verity enabled. >> It cannot be written to, and all reads from it will be verified >> against a cryptographic hash that covers the >> entire file (e.g., via a Merkle tree). >> +.TP >> +.BR STATX_ATTR_DAX (since Linux 5.8) >> +The file is in the DAX (cpu direct access) state. DAX state attempts to >> +minimize software cache effects for both I/O and memory mappings of this file. >> +It requires a file system which has been configured to support DAX. >> +.PP >> +DAX generally assumes all accesses are via cpu load / store instructions which >> +can minimize overhead for small accesses, but may adversely affect cpu >> +utilization for large transfers. >> +.PP >> +File I/O is done directly to/from user-space buffers and memory mapped I/O may >> +be performed with direct memory mappings that bypass kernel page cache. >> +.PP >> +While the DAX property tends to result in data being transferred synchronously, >> +it does not give the same guarantees of O_SYNC where data and the necessary >> +metadata are transferred together. >> +.PP >> +A DAX file may support being mapped with the MAP_SYNC flag, which enables a >> +program to use CPU cache flush instructions to persist CPU store operations >> +without an explicit >> +.BR fsync(2). >> +See >> +.BR mmap(2) >> +for more information. >> .SH RETURN VALUE >> On success, zero is returned. >> On error, \-1 is returned, and >> -- >> 2.25.1 >> -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
