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8b418c83d1
* The sparsity check was ineffective: it compared the apparent size in bytes to the actual size in blocks. Instead, write a tool that reliably detects sparseness. * Some of the seq commands were missing an argument. * Based on empirical evidence, 1 MB holes are not necessarily large enough to be preserved by the underlying filesystem. Increase the hole size to 16 MB. MFC after: 1 week Sponsored by: Klara, Inc. Reviewed by: cracauer Differential Revision: https://reviews.freebsd.org/D38414
74 lines
1.2 KiB
C
74 lines
1.2 KiB
C
/*-
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* Copyright (c) 2023 Klara, Inc.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <err.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sysexits.h>
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#include <unistd.h>
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static bool verbose;
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/*
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* Returns true if the file named by its argument is sparse, i.e. if
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* seeking to SEEK_HOLE returns a different value than seeking to
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* SEEK_END.
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*/
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static bool
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sparse(const char *filename)
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{
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off_t hole, end;
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int fd;
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if ((fd = open(filename, O_RDONLY)) < 0 ||
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(hole = lseek(fd, 0, SEEK_HOLE)) < 0 ||
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(end = lseek(fd, 0, SEEK_END)) < 0)
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err(1, "%s", filename);
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close(fd);
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if (end > hole) {
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if (verbose)
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printf("%s: hole at %zu\n", filename, (size_t)hole);
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return (true);
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}
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return (false);
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}
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static void
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usage(void)
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{
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fprintf(stderr, "usage: sparse [-v] file [...]\n");
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exit(EX_USAGE);
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}
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int
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main(int argc, char *argv[])
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{
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int opt, rv;
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while ((opt = getopt(argc, argv, "v")) != -1) {
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switch (opt) {
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case 'v':
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verbose = true;
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break;
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default:
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usage();
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break;
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}
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}
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argc -= optind;
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argv += optind;
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if (argc == 0)
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usage();
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rv = EXIT_SUCCESS;
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while (argc-- > 0)
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if (!sparse(*argv++))
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rv = EXIT_FAILURE;
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exit(rv);
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}
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