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fs: get rid of silly base class that causes build failures now

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The base class thing was an ugly way to get around the lack of C99
compound literals in C++, and also to make the bare ioctls usable with
the derived classes.

Today, both clang and gcc have C99 compound literals, so there's no need
to do crazy things with memset.  We never used the derived classes for
ioctls, and for this specific ioctl it would have been a very, very bad
idea, so there's no need to support that either.  We do need to jump
through hoops for ostream& operator<<() but we had to do those anyway
as there are other members in the derived type.

So we can simply drop the base class, and build the args object on the
stack in `do_ioctl`.  This also removes the need to verify initialization.

There's no bug here since the `info` member of the base class was
never used in place by the derived class, but new compilers reject the
flexible array member in the base class because the derived class makes
`info` be not at the end of the struct any more:

	error: flexible array member btrfs_ioctl_same_args::info not at end of struct crucible::BtrfsExtentSame

Fixes: https://github.com/Zygo/bees/issues/232
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2022-10-09 18:25:52 -04:00
parent dffd6e0b13
commit 14ce81c081
2 changed files with 12 additions and 14 deletions
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4
include/crucible/fs.h
View File

@ -31,12 +31,14 @@ namespace crucible {
BtrfsExtentInfo(int dst_fd, off_t dst_offset);
};
struct BtrfsExtentSame : public btrfs_ioctl_same_args {
struct BtrfsExtentSame {
virtual ~BtrfsExtentSame();
BtrfsExtentSame(int src_fd, off_t src_offset, off_t src_length);
void add(int fd, off_t offset);
virtual void do_ioctl();
uint64_t m_logical_offset = 0;
uint64_t m_length = 0;
int m_fd;
vector<BtrfsExtentInfo> m_info;
};

22
lib/fs.cc
View File

@ -45,13 +45,10 @@ namespace crucible {
}
BtrfsExtentSame::BtrfsExtentSame(int src_fd, off_t src_offset, off_t src_length) :
btrfs_ioctl_same_args( (btrfs_ioctl_same_args) { } ),
m_logical_offset(src_offset),
m_length(src_length),
m_fd(src_fd)
{
assert(logical_offset == 0);
assert(length == 0);
logical_offset = src_offset;
length = src_length;
}
BtrfsExtentSame::~BtrfsExtentSame()
@ -118,11 +115,8 @@ namespace crucible {
os << " '" << fd_name << "'";
});
}
os << ", .logical_offset = " << to_hex(bes.logical_offset);
os << ", .length = " << to_hex(bes.length);
os << ", .dest_count = " << bes.dest_count;
os << ", .reserved1 = " << bes.reserved1;
os << ", .reserved2 = " << bes.reserved2;
os << ", .logical_offset = " << to_hex(bes.m_logical_offset);
os << ", .length = " << to_hex(bes.m_length);
os << ", .info[] = {";
for (size_t i = 0; i < bes.m_info.size(); ++i) {
os << " [" << i << "] = " << &(bes.m_info[i]) << ",";
@ -145,9 +139,11 @@ namespace crucible {
void
BtrfsExtentSame::do_ioctl()
{
dest_count = m_info.size();
const size_t buf_size = sizeof(btrfs_ioctl_same_args) + dest_count * sizeof(btrfs_ioctl_same_extent_info);
ByteVector ioctl_arg(static_cast<btrfs_ioctl_same_args&>(*this), buf_size);
const size_t buf_size = sizeof(btrfs_ioctl_same_args) + m_info.size() * sizeof(btrfs_ioctl_same_extent_info);
ByteVector ioctl_arg( (btrfs_ioctl_same_args) {
.logical_offset = m_logical_offset,
.length = m_length,
}, buf_size);
btrfs_ioctl_same_args *const ioctl_ptr = ioctl_arg.get<btrfs_ioctl_same_args>();
size_t count = 0;
for (auto i = m_info.cbegin(); i != m_info.cend(); ++i) {