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c74fbaefeb
Remove the optimization that avoided up to 50% of cp's read syscalls.
Do not assume that a short read on a regular file indicates EOF.
When reading from a file in /proc on linux [at least 2.6.9 - 2.6.29]
into a 4k-byte buffer or larger, a short read does not
always indicate EOF. For example, "cp /proc/slabinfo /tmp"
copies only 4068 of the total 7493 bytes. This optimization
(25719a3315, Improve performance a bit
by optimizing away; 2005-11-24) appears to have been worth less than
a 2% speed-up (and usually much less), so the impact of removing it
is negligible.
* src/copy.c (copy_reg): Don't exit the loop early.
* tests/cp/proc-short-read: New test, lightly based on a suggestion
from Mike Frysinger, to exercise this fix.
* tests/Makefile.am (TESTS): Add cp/proc-short-read.
* NEWS (Improve robustness): Mention this change.
46 lines
1.3 KiB
Bash
Executable File
46 lines
1.3 KiB
Bash
Executable File
#!/bin/sh
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# exercise cp's short-read failure when operating on >4KB files in /proc
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# Copyright (C) 2009 Free Software Foundation, Inc.
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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if test "$VERBOSE" = yes; then
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set -x
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cp --version
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fi
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. $srcdir/test-lib.sh
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fail=0
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kall=/proc/kallsyms
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test -r $kall || skip_test_ "your system lacks $kall"
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# Before coreutils-7.3, cp would copy less than 4KiB of this 1MB+ file.
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cp $kall 1 || fail=1
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cat $kall > 2 || fail=1
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compare 1 2 || fail=1
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# Also check md5sum, just for good measure.
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md5sum $kall > 3 || fail=1
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md5sum 2 > 4 || fail=1
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# Remove each file name before comparing checksums.
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sed 's/ .*//' 3 > sum.proc || fail=1
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sed 's/ .*//' 4 > sum.2 || fail=1
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compare sum.proc sum.2 || fail=1
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Exit $fail
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