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extentwalker: fix the hole position logic

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When a file ends with a hole, ExtentWalker synthesizes a hole extent record
to cover the distance between the last ipos and EOF.  Unfortunately, ipos
was incremented by the number of items in the result vector instead.  Fix
that by incrementing by hole_extent.size().

While we're here, fix up some of the other data quality logic, including
a useless THROW_CHECK that was nothing but workarounds for earlier bugs.

Fixes: https://github.com/Zygo/bees/issues/26
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2018-01-29 16:30:07 -05:00
parent 1fd26a03b2
commit 52279656cf
1 changed files with 11 additions and 6 deletions
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17
lib/extentwalker.cc
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@ -299,6 +299,11 @@ namespace crucible {
while (fmi != fm.end()) {
Extent new_extent(*fmi);
THROW_CHECK2(runtime_error, ipos, new_extent.m_begin, ipos <= new_extent.m_begin);
// Don't map extents past EOF, we can't read them
if (new_extent.m_begin >= m_stat.st_size) {
last_extent_is_last = true;
break;
}
if (new_extent.m_begin > ipos) {
Extent hole_extent;
hole_extent.m_begin = ipos;
@ -326,13 +331,13 @@ namespace crucible {
hole_extent.m_flags |= FIEMAP_EXTENT_LAST;
}
new_vec.push_back(hole_extent);
ipos += new_vec.size();
ipos += hole_extent.size();
}
// Extent list must now be non-empty, at least a hole
THROW_CHECK1(runtime_error, new_vec.size(), !new_vec.empty());
// Allow last extent to extend beyond desired range (e.g. at EOF)
// ...but that's not what this does
// THROW_CHECK3(runtime_error, ipos, new_vec.rbegin()->m_end, m_stat.st_size, ipos <= new_vec.rbegin()->m_end);
// ipos must match end of last extent
THROW_CHECK3(runtime_error, ipos, new_vec.rbegin()->m_end, m_stat.st_size, ipos == new_vec.rbegin()->m_end);
// If we have the last extent in the file, truncate it to the file size.
if (ipos >= m_stat.st_size) {
@ -341,9 +346,10 @@ namespace crucible {
new_vec.rbegin()->m_end = m_stat.st_size;
}
// Verify contiguous, ascending order, at least one Extent
// Verify at least one Extent
THROW_CHECK1(runtime_error, new_vec, !new_vec.empty());
// Verify contiguous, ascending order, only extent with FIEMAP_EXTENT_LAST flag is the last extent
ipos = new_vec.begin()->m_begin;
bool last_flag_last = false;
for (auto e : new_vec) {
@ -353,7 +359,6 @@ namespace crucible {
ipos += e.size();
last_flag_last = e.m_flags & FIEMAP_EXTENT_LAST;
}
THROW_CHECK1(runtime_error, new_vec, !last_extent_is_last || new_vec.rbegin()->m_end == ipos);
m_extents = new_vec;
m_current = m_extents.begin();