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pack-object: tolerate broken packs that have duplicated objects

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When --reuse-delta is in effect (which is the default), and an existing
pack in the repository has the same object registered twice (e.g. one copy
in a non-delta format and the other copy in a delta against some other
object), an attempt to repack the repository can result in a cyclic delta
dependency, causing write_one() function to infinitely recurse into
itself.

Detect such a case and break the loopy dependency by writing out an object
that is involved in such a loop in the non-delta format.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2011-11-16 22:04:03 -08:00
parent 6320526415
commit f63c79dbc8
1 changed files with 43 additions and 12 deletions
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55
builtin/pack-objects.c
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@ -404,25 +404,56 @@ static unsigned long write_object(struct sha1file *f,
return hdrlen + datalen;
}
static int write_one(struct sha1file *f,
struct object_entry *e,
off_t *offset)
enum write_one_status {
WRITE_ONE_SKIP = -1, /* already written */
WRITE_ONE_BREAK = 0, /* writing this will bust the limit; not written */
WRITE_ONE_WRITTEN = 1, /* normal */
WRITE_ONE_RECURSIVE = 2 /* already scheduled to be written */
};
static enum write_one_status write_one(struct sha1file *f,
struct object_entry *e,
off_t *offset)
{
unsigned long size;
int recursing;
/* offset is non zero if object is written already. */
if (e->idx.offset || e->preferred_base)
return -1;
/*
* we set offset to 1 (which is an impossible value) to mark
* the fact that this object is involved in "write its base
* first before writing a deltified object" recursion.
*/
recursing = (e->idx.offset == 1);
if (recursing) {
warning("recursive delta detected for object %s",
sha1_to_hex(e->idx.sha1));
return WRITE_ONE_RECURSIVE;
} else if (e->idx.offset || e->preferred_base) {
/* offset is non zero if object is written already. */
return WRITE_ONE_SKIP;
}
/* if we are deltified, write out base object first. */
if (e->delta && !write_one(f, e->delta, offset))
return 0;
if (e->delta) {
e->idx.offset = 1; /* now recurse */
switch (write_one(f, e->delta, offset)) {
case WRITE_ONE_RECURSIVE:
/* we cannot depend on this one */
e->delta = NULL;
break;
default:
break;
case WRITE_ONE_BREAK:
e->idx.offset = recursing;
return WRITE_ONE_BREAK;
}
}
e->idx.offset = *offset;
size = write_object(f, e, *offset);
if (!size) {
e->idx.offset = 0;
return 0;
e->idx.offset = recursing;
return WRITE_ONE_BREAK;
}
written_list[nr_written++] = &e->idx;
@ -430,7 +461,7 @@ static int write_one(struct sha1file *f,
if (signed_add_overflows(*offset, size))
die("pack too large for current definition of off_t");
*offset += size;
return 1;
return WRITE_ONE_WRITTEN;
}
static void write_pack_file(void)
@ -468,7 +499,7 @@ static void write_pack_file(void)
offset = sizeof(hdr);
nr_written = 0;
for (; i < nr_objects; i++) {
if (!write_one(f, objects + i, &offset))
if (write_one(f, objects + i, &offset) == WRITE_ONE_BREAK)
break;
display_progress(progress_state, written);
}