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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