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Add O_DIRECT flag to DD for cache bypass 

FreeBSD DD utility has not had support for the O_DIRECT flag, which
is useful to bypass local caching, e.g. for unconditionally issuing
NFS IO requests during testing.

Reviewed by:	rgrimes (mentor)
Approved by:	rgrimes (mentor, blanket)
MFC after:	3 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25066
This commit is contained in:
Richard Scheffenegger 2020-06-04 20:47:11 +00:00
parent 51569bd793
commit f4b4526f23
4 changed files with 17 additions and 4 deletions
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2
bin/dd/args.c
View File

@ -266,6 +266,7 @@ static const struct iflag {
const char *name;
uint64_t set, noset;
} ilist[] = {
{ "direct", C_IDIRECT, 0 },
{ "fullblock", C_IFULLBLOCK, C_SYNC },
};
@ -410,6 +411,7 @@ static const struct oflag {
const char *name;
uint64_t set;
} olist[] = {
{ "direct", C_ODIRECT },
{ "fsync", C_OFSYNC },
{ "sync", C_OFSYNC },
};

8
bin/dd/dd.1
View File

@ -32,7 +32,7 @@
.\" @(#)dd.1 8.2 (Berkeley) 1/13/94
.\" $FreeBSD$
.\"
.Dd March 26, 2019
.Dd June 4, 2020
.Dt DD 1
.Os
.Sh NAME
@ -117,6 +117,8 @@ limits the number of times
is called on the input rather than the number of blocks copied in full.
May not be combined with
.Cm conv=sync .
.It Cm direct
Set the O_DIRECT flag on the input file to make reads bypass any local caching.
.El
.It Cm iseek Ns = Ns Ar n
Seek on the input file
@ -143,7 +145,7 @@ the output file is truncated at that point.
Where
.Cm value
is one of the symbols from the following list.
.Bl -tag -width "fsync"
.Bl -tag -width "direct"
.It Cm fsync
Set the O_FSYNC flag on the output file to make writes synchronous.
.It Cm sync
@ -151,6 +153,8 @@ Set the O_SYNC flag on the output file to make writes synchronous.
This is synonymous with the
.Cm fsync
value.
.It Cm direct
Set the O_DIRECT flag on the output file to make writes bypass any local caching.
.El
.It Cm oseek Ns = Ns Ar n
Seek on the output file

9
bin/dd/dd.c
View File

@ -143,7 +143,7 @@ static void
setup(void)
{
u_int cnt;
int oflags;
int iflags, oflags;
cap_rights_t rights;
unsigned long cmds[] = { FIODTYPE, MTIOCTOP };
@ -151,7 +151,10 @@ setup(void)
in.name = "stdin";
in.fd = STDIN_FILENO;
} else {
in.fd = open(in.name, O_RDONLY, 0);
iflags = 0;
if (ddflags & C_IDIRECT)
iflags |= O_DIRECT;
in.fd = open(in.name, O_RDONLY | iflags, 0);
if (in.fd == -1)
err(1, "%s", in.name);
}
@ -186,6 +189,8 @@ setup(void)
oflags |= O_TRUNC;
if (ddflags & C_OFSYNC)
oflags |= O_FSYNC;
if (ddflags & C_ODIRECT)
oflags |= O_DIRECT;
out.fd = open(out.name, O_RDWR | oflags, DEFFILEMODE);
/*
* May not have read access, so try again with write only.

2
bin/dd/dd.h
View File

@ -105,6 +105,8 @@ typedef struct {
#define C_FDATASYNC 0x0000000100000000ULL
#define C_OFSYNC 0x0000000200000000ULL
#define C_IFULLBLOCK 0x0000000400000000ULL
#define C_IDIRECT 0x0000000800000000ULL
#define C_ODIRECT 0x0000001000000000ULL
#define C_PARITY (C_PAREVEN | C_PARODD | C_PARNONE | C_PARSET)