Messages in this thread Patch in this message | | | Date | Wed, 7 Apr 2004 12:31:16 -0500 | From | Andy Isaacson <> | Subject | Re: dd PATCH: add conv=direct |
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On Tue, Apr 06, 2004 at 05:33:26PM -0700, Andrew Morton wrote: > Andy Isaacson <adi@hexapodia.org> wrote: > > dd(1) is convenient for this purpose, but is lacking a method > > to force O_DIRECT. The enclosed patch adds a "conv=direct" flag to > > enable this usage. > > This would be rather nice to have. You'll need to ensure that the data > is page-aligned in memory.
So, some confusion on my part about O_DIRECT: I can't get O_DIRECT to work on ext3, at all, on 2.4.25 -- open(O_DIRECT) succeeds, but the write returns EINVAL. Same code works fine when writing to a block device. If the problem is that ext3 can't support O_DIRECT, why does the open succeed?
> While you're there, please add an fsync-before-closing option.
Easy enough. How does this look? Note that C_TWOBUFS ensures the output buffer is getpagesize()-aligned.
The next feature to add would be OpenBSD-style "KB/s" reporting. I'm not going there.
-andy
2004-04-07 Andy Isaacson <adi@hexapodia.org>
* add conv=direct and conv=fsync options.
diff -ur coreutils-5.0.91/doc/coreutils.texi coreutils-5.0.91-adi/doc/coreutils.texi --- coreutils-5.0.91/doc/coreutils.texi 2003-09-04 16:26:51.000000000 -0500 +++ coreutils-5.0.91-adi/doc/coreutils.texi 2004-04-07 11:26:36.000000000 -0500 @@ -6373,6 +6373,16 @@ Pad every input block to size of @samp{ibs} with trailing zero bytes. When used with @samp{block} or @samp{unblock}, pad with spaces instead of zero bytes. + +@item fsync +@opindex fsync +Call @samp{fsync(2)} on the output file before exiting. This ensures +that the file data is written to permanent store. + +@item direct +@opindex direct +Open the output file with O_DIRECT, avoiding (on Linux) using the buffer +cache. @end table @end table diff -ur coreutils-5.0.91/src/dd.c coreutils-5.0.91-adi/src/dd.c --- coreutils-5.0.91/src/dd.c 2003-07-25 02:43:09.000000000 -0500 +++ coreutils-5.0.91-adi/src/dd.c 2004-04-07 11:45:23.000000000 -0500 @@ -66,6 +66,9 @@ /* Default input and output blocksize. */ #define DEFAULT_BLOCKSIZE 512 +/* XXX hack */ +#define HAVE_O_DIRECT 1 + /* Conversions bit masks. */ #define C_ASCII 01 #define C_EBCDIC 02 @@ -78,6 +81,8 @@ #define C_NOERROR 0400 #define C_NOTRUNC 01000 #define C_SYNC 02000 +#define C_FSYNC 010000 +#define C_DIRECT 020000 /* Use separate input and output buffers, and combine partial input blocks. */ #define C_TWOBUFS 04000 @@ -162,6 +167,10 @@ {"noerror", C_NOERROR}, /* Ignore i/o errors. */ {"notrunc", C_NOTRUNC}, /* Do not truncate output file. */ {"sync", C_SYNC}, /* Pad input records to ibs with NULs. */ + {"fsync", C_FSYNC}, /* call fsync(2) before closing output file */ +#ifdef HAVE_O_DIRECT + {"direct", C_DIRECT | C_TWOBUFS}, /* open files with O_DIRECT */ +#endif {NULL, 0} }; @@ -1190,6 +1199,11 @@ = (O_CREAT | (seek_records || (conversions_mask & C_NOTRUNC) ? 0 : O_TRUNC)); +#if HAVE_O_DIRECT + if (conversions_mask & C_DIRECT) + opts |= O_DIRECT; +#endif + /* Open the output file with *read* access only if we might need to read to satisfy a `seek=' request. If we can't read the file, go ahead with write-only access; it might work. */ @@ -1240,5 +1254,11 @@ exit_status = dd_copy (); + if (conversions_mask & C_FSYNC) + { + if (fsync (STDOUT_FILENO) != 0) + error(0, errno, _("cannot fsync %s"), quote (output_file)); + } + quit (exit_status); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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