mirror of
https://github.com/trapexit/mergerfs.git
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cb33f39a61
- 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.
105 lines
2.8 KiB
C++
105 lines
2.8 KiB
C++
/*
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ISC License
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Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "fuse_readdir_cor.hpp"
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#include "supported_getdents64.hpp"
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#include "config.hpp"
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#include "dirinfo.hpp"
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#include "error.hpp"
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FUSE::ReadDirCOR::ReadDirCOR(unsigned concurrency_,
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unsigned max_queue_depth_)
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: _tp(concurrency_,max_queue_depth_,"readdir.cor")
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{
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}
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FUSE::ReadDirCOR::~ReadDirCOR()
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{
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}
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#ifdef MERGERFS_SUPPORTED_GETDENTS64
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#include "fuse_readdir_cor_getdents.icpp"
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#else
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#include "fuse_readdir_cor_readdir.icpp"
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#endif
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// Uses a per-call mutex. Lifetime is one readdir operation. It
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// serializes the dirent-merge step (dedup'ing of names + append to
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// dirents list) across at-most-branches-worth of parallel worker
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// tasks. Per-branch opendir + getdents64 run fully outside the
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// critical section, so the lock holds only long enough to merge each
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// batch.
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static
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inline
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int
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_concurrent_readdir(ThreadPool &tp_,
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const Branches::Ptr branches_,
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const fs::path &rel_dirpath_,
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fuse_dirents_t *dirents_)
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{
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HashSet names;
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Mutex mutex;
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std::vector<std::future<int>> futures;
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fuse_dirents_reset(dirents_);
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futures.reserve(branches_->size());
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for(const auto &branch : *branches_)
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{
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auto func =
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[&,dirents_]()
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{
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return ::_readdir(branch.path,
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rel_dirpath_,
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names,
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dirents_,
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mutex);
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};
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auto rv = tp_.enqueue_task(std::move(func));
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futures.emplace_back(std::move(rv));
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}
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Err err;
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for(auto &future : futures)
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err = future.get();
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return err;
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}
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int
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FUSE::ReadDirCOR::operator()(const fuse_req_ctx_t *ctx_,
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const fuse_file_info_t *ffi_,
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fuse_dirents_t *dirents_)
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{
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DirInfo *di = DirInfo::from_fh(ffi_->fh);
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if(not di)
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return -EBADF;
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return ::_concurrent_readdir(_tp,
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cfg.branches,
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di->fusepath,
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dirents_);
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}
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