- Expose the ioprio enabled flag as an atomic for relaxed inline checks
- Inline SetFrom construction so disabled read/write paths avoid a function call
- Move priority application into a slow helper used only when ioprio is enabled
- Replace atomic shared pointer loads/stores with shared/unique locking.
- Store the configured readdir mode directly as std::string.
- Copy the active ReadDir implementation under lock before invoking it.
- Use relaxed increment under the map bucket lock when duplicating file handles.
- Use acq_rel decrement when releasing and checking for final references.
- Load moved ref_count with relaxed ordering during map insertion.
- Explain that the mutex is per readdir call.
- Document that only dirent deduplication and list append are serialized.
- Clarify that per-branch opendir and getdents64 work runs outside the critical section.
- Replace the per-file Mutex with std::shared_mutex for shared write access.
- Run direct and cached writes under a shared lock while the fd is stable.
- Retry failed writes under a unique lock before move-on-ENOSPC relocation.
Important changes:
- Switch mergerfs and vendored libfuse Makefiles to -std=c++20.
- Select the latest available GCC/G++ or toolset in container builds.
- Verify compiler C++20 support during package installation.
- Fix dynamic SysLog formatting for fmt C++20 checks.
No functional change: libfuse/helper.cpp (fuse_daemonize,
fuse_helper_opt_proc, fuse_parse_cmdline) and mergerfs
fuse_init.cpp (_want helpers) reformatted to match the project's
GNU-style brace placement and aligned parameter lists.
libfuse previously initialized its debug log filepath to
"/dev/stderr", forcing the config layer to reopen stderr on every
load whether or not the user asked for it. Default the libfuse log
path to "" and have the mergerfs config layer only forward the
request to libfuse when the user supplied an explicit path.
Both helpers previously called strcmp/pointer-dereference directly
on their arguments, so a stray NULL (e.g. an unset env string or an
absent xattr) crashed the process. Guard both helpers: same()
returns true only if both pointers are equal, startswith() returns
false if either side is NULL.
The create policy can legitimately return success with an empty
destination list (e.g. every candidate rejected). Previously we
then dereferenced dst_branch[0] and faulted. Return -ENOSPC so the
original write that triggered the move propagates a sensible errno
to userspace.
The branch-aggregation code computed
blocks * f_frsize / min_frsize
as u64 arithmetic. With large filesystems the intermediate product
blocks * f_frsize overflows 64 bits long before the division can
bring the result back into range, producing garbage bavail/bfree
values reported to userspace.
Compute the scale factor once in long double and multiply each
count by it, so the only narrowing happens in the final cast back
to fsblkcnt_t.
Old code only null-terminated when the returned/copied length was
strictly less than the caller-supplied bufsize_, leaving the buffer
unterminated on an exact-fill. Since buf_ is consumed as a C string,
reserve one byte for the terminator up front and unconditionally
terminate.
- ReadDir::_initialized is set by the first thread through the
lazy-init path and read by every subsequent caller; make it
std::atomic<bool> so the read/write pair has a happens-before
relationship.
- The 'no valid mergerfs branch found' error directory entry used
strcpy into a fixed-size dirent buffer. The message happens to
fit today but the buffer is only NAME_MAX wide; switch to a
length-bounded strncpy driven by the constexpr string size.
- The getdents implementations for seq/cor/cosr allocated a msgbuf
without checking for allocation failure and then dereferenced it.
Return -ENOMEM when the allocation fails.
The fake-root and control-file fast paths returned a synthetic stat
without touching the timeout struct. Callers that took those paths
ended up sending whatever the timeout struct happened to hold,
which is uninitialized memory for the control-file path and
whatever a prior call left there for the fake-root path. Kernel
behavior is undefined when the timeout is garbage.
Pass timeout_ into both helpers and set entry/attr from the
configured cache values.
Previously most FUSE ops took a reference to the live cfg.branches
object. With atomic_load now producing a shared_ptr snapshot, pass
it by value: the op works against a single stable view of the
configuration for its whole lifetime, immune to concurrent
reconfiguration.
Also bail out with -ENOENT when the policy returns an empty branch
set rather than dereferencing branches[0]. This was reachable if a
policy rejected every branch (e.g. everything readonly while
looking for a writable target).
Covers access, chmod, chown, create, getattr, getxattr, ioctl,
link, listxattr, mkdir, mknod, open, readdir (cor/cosr),
readlink, removexattr, rename, rmdir, setxattr, statfs, statx,
symlink, truncate, unlink, utimens.
While here, in _getattr only dereference st_->st_mode when lstat
succeeded (it is otherwise uninitialized).
Several FUSE ops fell back to looking up a FileInfo via
state.open_files when the kernel-provided fh was zero, returning
-ENOENT if the lookup failed. This path papered over handle-tracking
bugs and added cost on every call. Use the handle directly and
return -EBADF when it is invalid - the kernel should always hand us
a valid fh for an open resource.
Also simplify FileInfo::from_fh / DirInfo::from_fh and their to_fh
helpers: callers now handle the null-pointer case explicitly so the
ASSERT_NOT_NULL checks are redundant.
Covers fallocate, fchmod, fchown, fgetattr, flock, ftruncate,
futimens, read, release, releasedir, write, statx, ioctl (file +
dir), readdir (sequential, concurrent-on-read,
concurrent-on-search), and the passthrough fast paths in
create/open.
Branches using the default minfreespace held a reference to their
owning Impl's _default_minfreespace. After a copy or move the
pointer still referenced the source Impl, which could become
invalid or diverge after further configuration changes. Switch to
a pointer and re-link it to the destination Impl on copy/move.
While here, convert set_branch_mode to do an atomic_store of a
newly constructed Impl rather than mutating the shared pointer
target in place. Readers holding an atomic_load snapshot are no
longer affected by a concurrent mode change.
ref_count is read and written from multiple FUSE worker threads
during open/release. Make it std::atomic<int> and provide a move
constructor so OpenFile remains movable when the underlying atomic
is non-movable.
rwlock.hpp was left over after migrating to atomic shared pointers
for branches configuration. No code references ReadGuard/WriteGuard
any longer, so drop the header and its stale includes.
Antonio SJ Musumeci