fix(rm): keep directory FD use O(1) on deep trees#13420
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Recursive rm held one DirFd per nesting level, so deep trees failed with EMFILE under normal NOFILE limits while GNU rm succeeded. Walk directories with an explicit stack, close the parent DirFd before descending, and reopen it from the saved path when returning to unlink. Preserves openat/unlinkat safety and adds a low-NOFILE regression test. Fixes uutils#7995 Signed-off-by: Alex Chen <l46983284@gmail.com>
Signed-off-by: Alex Chen <l46983284@gmail.com>
Merging this PR will degrade performance by 6.11%
|
| Mode | Benchmark | BASE |
HEAD |
Efficiency | |
|---|---|---|---|---|---|
| ❌ | Simulation | rm_recursive_tree |
12 ms | 13 ms | -7.69% |
| ❌ | Simulation | complex_relative_date |
137.2 µs | 147.9 µs | -7.21% |
| ❌ | Simulation | du_max_depth_balanced_tree[(6, 4, 10)] |
25.2 ms | 26.1 ms | -3.36% |
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Comparing l46983284-cpu:fix/rm-deep-tree-emfile (bcda98a) with main (9846eb8)
Footnotes
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46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
Flip child_error branch for clippy::if_not_else and reword the doc comment so cspell does not flag EMFILE. Signed-off-by: Alex Chen <l46983284@gmail.com>
Use cargo fmt import order (CI) and else-if chain for clippy if_not_else / collapsible_else_if cleanliness. Signed-off-by: Alex Chen <l46983284@gmail.com>
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Summary
rm -ron a very deep directory tree fails withToo many open files(EMFILE) while GNUrmsucceeds. Recursive safe traversal kept oneDirFdopen per nesting level, so FD use grew with depth.This change walks the tree with an explicit stack, closes the parent directory descriptor before descending, and reopens it from the saved path when returning to unlink the child.
openat/unlinkatsafety is preserved; open-file use stays O(1) with depth.Test plan
cargo build -p uu_rm --releaseprlimit --nofile=32removes successfullytests/by-util/test_rm.rsincluding newtest_rm_recursive_deep_tree_low_nofile(NOFILE=32, depth 80)Fixes #7995