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Fix lseek(SEEK_DATA/SEEK_HOLE) mmap consistency
When using lseek(2) to report data/holes memory mapped regions of the file were ignored. This could result in incorrect results. To handle this zfs_holey_common() was updated to asynchronously writeback any dirty mmap(2) regions prior to reporting holes. Additionally, while not strictly required, the dn_struct_rwlock is now held over the dirty check to prevent the dnode structure from changing. This ensures that a clean dnode can't be dirtied before the data/hole is located. The range lock is now also taken to ensure the call cannot race with zfs_write(). Furthermore, the code was refactored to provide a dnode_is_dirty() helper function which checks the dnode for any dirty records to determine its dirtiness. Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Rich Ercolani <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #11900 Closes #12724
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| /mmap_seek |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,6 @@ | ||
| include $(top_srcdir)/config/Rules.am | ||
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| pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/bin | ||
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| pkgexec_PROGRAMS = mmap_seek | ||
| mmap_seek_SOURCES = mmap_seek.c |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,147 @@ | ||
| /* | ||
| * CDDL HEADER START | ||
| * | ||
| * The contents of this file are subject to the terms of the | ||
| * Common Development and Distribution License (the "License"). | ||
| * You may not use this file except in compliance with the License. | ||
| * | ||
| * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE | ||
| * or http://www.opensolaris.org/os/licensing. | ||
| * See the License for the specific language governing permissions | ||
| * and limitations under the License. | ||
| * | ||
| * When distributing Covered Code, include this CDDL HEADER in each | ||
| * file and include the License file at usr/src/OPENSOLARIS.LICENSE. | ||
| * If applicable, add the following below this CDDL HEADER, with the | ||
| * fields enclosed by brackets "[]" replaced with your own identifying | ||
| * information: Portions Copyright [yyyy] [name of copyright owner] | ||
| * | ||
| * CDDL HEADER END | ||
| */ | ||
|
|
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| /* | ||
| * Copyright (c) 2021 by Lawrence Livermore National Security, LLC. | ||
| */ | ||
|
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| #include <unistd.h> | ||
| #include <fcntl.h> | ||
| #include <stdio.h> | ||
| #include <stdlib.h> | ||
| #include <string.h> | ||
| #include <sys/mman.h> | ||
| #include <errno.h> | ||
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| static void | ||
| seek_data(int fd, off_t offset, off_t expected) | ||
| { | ||
| off_t data_offset = lseek(fd, offset, SEEK_DATA); | ||
| if (data_offset != expected) { | ||
| fprintf(stderr, "lseek(fd, %d, SEEK_DATA) = %d (expected %d)\n", | ||
| (int)offset, (int)data_offset, (int)expected); | ||
| exit(2); | ||
| } | ||
| } | ||
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| static void | ||
| seek_hole(int fd, off_t offset, off_t expected) | ||
| { | ||
| off_t hole_offset = lseek(fd, offset, SEEK_HOLE); | ||
| if (hole_offset != expected) { | ||
| fprintf(stderr, "lseek(fd, %d, SEEK_HOLE) = %d (expected %d)\n", | ||
| (int)offset, (int)hole_offset, (int)expected); | ||
| exit(2); | ||
| } | ||
| } | ||
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| int | ||
| main(int argc, char **argv) | ||
| { | ||
| char *execname = argv[0]; | ||
| char *file_path = argv[1]; | ||
| char *buf = NULL; | ||
| int err; | ||
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| if (argc != 4) { | ||
| (void) printf("usage: %s <file name> <file size> " | ||
| "<block size>\n", argv[0]); | ||
| exit(1); | ||
| } | ||
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| int fd = open(file_path, O_RDWR | O_CREAT, 0666); | ||
| if (fd == -1) { | ||
| (void) fprintf(stderr, "%s: %s: ", execname, file_path); | ||
| perror("open"); | ||
| exit(2); | ||
| } | ||
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| off_t file_size = atoi(argv[2]); | ||
| off_t block_size = atoi(argv[3]); | ||
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| if (block_size * 2 > file_size) { | ||
| (void) fprintf(stderr, "file size must be at least " | ||
| "double the block size\n"); | ||
| exit(2); | ||
| } | ||
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| err = ftruncate(fd, file_size); | ||
| if (err == -1) { | ||
| perror("ftruncate"); | ||
| exit(2); | ||
| } | ||
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| if ((buf = mmap(NULL, file_size, PROT_READ | PROT_WRITE, | ||
| MAP_SHARED, fd, 0)) == MAP_FAILED) { | ||
| perror("mmap"); | ||
| exit(2); | ||
| } | ||
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| /* Verify the file is sparse and reports no data. */ | ||
| seek_data(fd, 0, -1); | ||
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| /* Verify the file is reported as a hole. */ | ||
| seek_hole(fd, 0, 0); | ||
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| /* Verify search beyond end of file is an error. */ | ||
| seek_data(fd, 2 * file_size, -1); | ||
| seek_hole(fd, 2 * file_size, -1); | ||
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| /* Dirty the first byte. */ | ||
| memset(buf, 'a', 1); | ||
| seek_data(fd, 0, 0); | ||
| seek_data(fd, block_size, -1); | ||
| seek_hole(fd, 0, block_size); | ||
| seek_hole(fd, block_size, block_size); | ||
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| /* Dirty the first half of the file. */ | ||
| memset(buf, 'b', file_size / 2); | ||
| seek_data(fd, 0, 0); | ||
| seek_data(fd, block_size, block_size); | ||
| seek_hole(fd, 0, P2ROUNDUP(file_size / 2, block_size)); | ||
| seek_hole(fd, block_size, P2ROUNDUP(file_size / 2, block_size)); | ||
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| /* Dirty the whole file. */ | ||
| memset(buf, 'c', file_size); | ||
| seek_data(fd, 0, 0); | ||
| seek_data(fd, file_size * 3 / 4, | ||
| P2ROUNDUP(file_size * 3 / 4, block_size)); | ||
| seek_hole(fd, 0, file_size); | ||
| seek_hole(fd, file_size / 2, file_size); | ||
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| /* Punch a hole (required compression be enabled). */ | ||
| memset(buf + block_size, 0, block_size); | ||
| seek_data(fd, 0, 0); | ||
| seek_data(fd, block_size, 2 * block_size); | ||
| seek_hole(fd, 0, block_size); | ||
| seek_hole(fd, block_size, block_size); | ||
| seek_hole(fd, 2 * block_size, file_size); | ||
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| err = munmap(buf, file_size); | ||
| if (err == -1) { | ||
| perror("munmap"); | ||
| exit(2); | ||
| } | ||
|
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| close(fd); | ||
|
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||
| return (0); | ||
| } |
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