svn: head/bin/dd
Maxim Sobolev
sobomax at FreeBSD.org
Fri Feb 19 06:12:57 UTC 2016
Thanks, Thomas. IMHO this is quite serious bug in one of the core
utilities, so I suggest it gets faster MFC before 10.3 goes into beta stage
on Feb 26. The old code in RELENG_10 is just plain broken anyway now, so it
could not make it any worse. Thanks!
On Thu, Feb 18, 2016 at 12:44 AM, Thomas Quinot <thomas at freebsd.org> wrote:
> Author: thomas
> Date: Thu Feb 18 08:44:16 2016
> New Revision: 295749
> URL: https://svnweb.freebsd.org/changeset/base/295749
>
> Log:
> Reorganize the handling all-zeroes terminal block in sparse mode
>
> The intent of the previous code in that case was to force
> an explicit write, but the implementation was incorrect, and
> as a result the write was never performed. This new implementation
> instead uses ftruncate(2) to extend the file with a trailing hole.
>
> Also introduce regression tests for these cases.
>
> PR: 189284
> (original PR whose fix introduced this bug)
>
> PR: 207092
>
> Differential Revision: D5248
> Reviewed by: sobomax,kib
> MFC after: 2 weeks
>
> Added:
> head/bin/dd/ref.obs_zeroes (contents, props changed)
> Modified:
> head/bin/dd/Makefile
> head/bin/dd/dd.c
> head/bin/dd/dd.h
> head/bin/dd/gen.c
>
> Modified: head/bin/dd/Makefile
>
> ==============================================================================
> --- head/bin/dd/Makefile Thu Feb 18 07:44:14 2016 (r295748)
> +++ head/bin/dd/Makefile Thu Feb 18 08:44:16 2016 (r295749)
> @@ -24,7 +24,18 @@ test: ${PROG} gen
> LC_ALL=en_US.US-ASCII hexdump -C | \
> diff -I FreeBSD - ${.CURDIR}/ref.${conv}
> .endfor
> - @rm -f gen
> + @${ECHO} "testing sparse file (obs zeroes)"
> + @./gen 189284 | ./dd ibs=16 obs=8 conv=sparse of=obs_zeroes 2>
> /dev/null
> + @hexdump -C obs_zeroes | diff -I FreeBSD -
> ${.CURDIR}/ref.obs_zeroes
> +
> + @${ECHO} "testing spase file (all zeroes)"
> + @./dd if=/dev/zero of=1M_zeroes bs=1048576 count=1 2> /dev/null
> + @./dd if=1M_zeroes of=1M_zeroes.1 bs=1048576 conv=sparse 2>
> /dev/null
> + @./dd if=1M_zeroes of=1M_zeroes.2 bs=1048576 2> /dev/null
> + @diff 1M_zeroes 1M_zeroes.1
> + @diff 1M_zeroes 1M_zeroes.2
> +
> + @rm -f gen 1M_zeroes* obs_zeroes
>
> .if ${MK_TESTS} != "no"
> SUBDIR+= tests
>
> Modified: head/bin/dd/dd.c
>
> ==============================================================================
> --- head/bin/dd/dd.c Thu Feb 18 07:44:14 2016 (r295748)
> +++ head/bin/dd/dd.c Thu Feb 18 08:44:16 2016 (r295749)
> @@ -77,7 +77,6 @@ STAT st; /* statistics */
> void (*cfunc)(void); /* conversion function */
> uintmax_t cpy_cnt; /* # of blocks to copy */
> static off_t pending = 0; /* pending seek if sparse */
> -static off_t last_sp = 0; /* size of last added sparse block */
> u_int ddflags = 0; /* conversion options */
> size_t cbsz; /* conversion block size */
> uintmax_t files_cnt = 1; /* # of files to copy */
> @@ -409,6 +408,15 @@ dd_close(void)
> }
> if (out.dbcnt || pending)
> dd_out(1);
> +
> + /*
> + * If the file ends with a hole, ftruncate it to extend its size
> + * up to the end of the hole (without having to write any data).
> + */
> + if (out.seek_offset > 0 && (out.flags & ISTRUNC)) {
> + if (ftruncate(out.fd, out.seek_offset) == -1)
> + err(1, "truncating %s", out.name);
> + }
> }
>
> void
> @@ -457,29 +465,27 @@ dd_out(int force)
> }
> if (sparse && !force) {
> pending += cnt;
> - last_sp = cnt;
> nw = cnt;
> } else {
> if (pending != 0) {
> - /* If forced to write, and we have
> no
> - * data left, we need to write the
> last
> - * sparse block explicitly.
> + /*
> + * Seek past hole. Note that we
> need to record the
> + * reached offset, because we
> might have no more data
> + * to write, in which case we'll
> need to call
> + * ftruncate to extend the file
> size.
> */
> - if (force && cnt == 0) {
> - pending -= last_sp;
> - assert(outp == out.db);
> - memset(outp, 0, cnt);
> - }
> - if (lseek(out.fd, pending,
> SEEK_CUR) ==
> - -1)
> + out.seek_offset = lseek(out.fd,
> pending, SEEK_CUR);
> + if (out.seek_offset == -1)
> err(2, "%s: seek error
> creating sparse file",
> out.name);
> - pending = last_sp = 0;
> + pending = 0;
> }
> - if (cnt)
> + if (cnt) {
> nw = write(out.fd, outp, cnt);
> - else
> + out.seek_offset = 0;
> + } else {
> return;
> + }
> }
>
> if (nw <= 0) {
>
> Modified: head/bin/dd/dd.h
>
> ==============================================================================
> --- head/bin/dd/dd.h Thu Feb 18 07:44:14 2016 (r295748)
> +++ head/bin/dd/dd.h Thu Feb 18 08:44:16 2016 (r295749)
> @@ -54,6 +54,7 @@ typedef struct {
> const char *name; /* name */
> int fd; /* file descriptor */
> off_t offset; /* # of blocks to skip */
> + off_t seek_offset; /* offset of last seek past output
> hole */
> } IO;
>
> typedef struct {
>
> Modified: head/bin/dd/gen.c
>
> ==============================================================================
> --- head/bin/dd/gen.c Thu Feb 18 07:44:14 2016 (r295748)
> +++ head/bin/dd/gen.c Thu Feb 18 08:44:16 2016 (r295749)
> @@ -5,13 +5,20 @@
> */
>
> #include <stdio.h>
> +#include <string.h>
>
> int
> -main(int argc __unused, char **argv __unused)
> +main(int argc, char **argv)
> {
> int i;
>
> - for (i = 0; i < 256; i++)
> - putchar(i);
> + if (argc > 1 && !strcmp(argv[1], "189284")) {
> + fputs("ABCDEFGH", stdout);
> + for (i = 0; i < 8; i++)
> + putchar(0);
> + } else {
> + for (i = 0; i < 256; i++)
> + putchar(i);
> + }
> return (0);
> }
>
> Added: head/bin/dd/ref.obs_zeroes
>
> ==============================================================================
> --- /dev/null 00:00:00 1970 (empty, because file is newly added)
> +++ head/bin/dd/ref.obs_zeroes Thu Feb 18 08:44:16 2016 (r295749)
> @@ -0,0 +1,3 @@
> +$FreeBSD$
> +00000000 41 42 43 44 45 46 47 48 00 00 00 00 00 00 00 00
> |ABCDEFGH........|
> +00000010
>
>
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