Patrick Williams | 92b42cb | 2022-09-03 06:53:57 -0500 | [diff] [blame^] | 1 | From 41574b628ec4229c24dfe289af7b6978edcca4ed Mon Sep 17 00:00:00 2001 |
| 2 | From: Sean Anderson <sean.anderson@seco.com> |
| 3 | Date: Thu, 30 Dec 2021 15:19:41 -0500 |
| 4 | Subject: [PATCH] libsparse: Add "hole" mode to sparse_file_read |
| 5 | |
| 6 | This adds support for filesystem-level sparse files. These files have |
| 7 | holes which are not stored in the filesystem and when read are full of |
| 8 | zeros. While these zeros may be significant in some types of files, |
| 9 | other types of files may not care about the contents of holes. For |
| 10 | example, most filesystem creation tools write to all the blocks they |
| 11 | care about. Those blocks not written to will remain holes, and can be |
| 12 | safely represented by "don't care" chunks. Using "don't care" chunks |
| 13 | instead of fill chunks can result in a substantial reduction of the time |
| 14 | it takes to program a sparse image. |
| 15 | |
| 16 | To accomplish this, we extend the existing "sparse" boolean parameter to |
| 17 | be an enum of mode types. This enum represents the strategy we take when |
| 18 | reading in a file. For the most part the implementation is |
| 19 | straightforward. We use lseek to determine where the holes in the file |
| 20 | are, and then use do_sparse_file_read_normal to create chunks for the |
| 21 | data section. Note that every file has an implicit hole at its end. |
| 22 | |
| 23 | Change-Id: I0cfbf08886fca9a91cb753ec8734c84fcbe52c9f |
| 24 | Upstream-Status: Backport [f96466b05543b984ef7315d830bab4a409228d35] |
| 25 | Signed-off-by: Sean Anderson <sean.anderson@seco.com> |
| 26 | --- |
| 27 | libsparse/img2simg.c | 2 +- |
| 28 | libsparse/include/sparse/sparse.h | 32 +++++++++++--- |
| 29 | libsparse/sparse_read.c | 71 +++++++++++++++++++++++++++++-- |
| 30 | 3 files changed, 93 insertions(+), 12 deletions(-) |
| 31 | |
| 32 | diff --git a/libsparse/img2simg.c b/libsparse/img2simg.c |
| 33 | index a0db36f45..2e171b613 100644 |
| 34 | --- a/libsparse/img2simg.c |
| 35 | +++ b/libsparse/img2simg.c |
| 36 | @@ -96,7 +96,7 @@ int main(int argc, char *argv[]) |
| 37 | } |
| 38 | |
| 39 | sparse_file_verbose(s); |
| 40 | - ret = sparse_file_read(s, in, false, false); |
| 41 | + ret = sparse_file_read(s, in, SPARSE_READ_MODE_NORMAL, false); |
| 42 | if (ret) { |
| 43 | fprintf(stderr, "Failed to read file\n"); |
| 44 | exit(-1); |
| 45 | diff --git a/libsparse/include/sparse/sparse.h b/libsparse/include/sparse/sparse.h |
| 46 | index 8b757d22a..b68aa21a8 100644 |
| 47 | --- a/libsparse/include/sparse/sparse.h |
| 48 | +++ b/libsparse/include/sparse/sparse.h |
| 49 | @@ -196,23 +196,41 @@ int64_t sparse_file_len(struct sparse_file *s, bool sparse, bool crc); |
| 50 | int sparse_file_callback(struct sparse_file *s, bool sparse, bool crc, |
| 51 | int (*write)(void *priv, const void *data, int len), void *priv); |
| 52 | |
| 53 | +/** |
| 54 | + * enum sparse_read_mode - The method to use when reading in files |
| 55 | + * @SPARSE_READ_MODE_NORMAL: The input is a regular file. Constant chunks of |
| 56 | + * data (including holes) will be be converted to |
| 57 | + * fill chunks. |
| 58 | + * @SPARSE_READ_MODE_SPARSE: The input is an Android sparse file. |
| 59 | + * @SPARSE_READ_MODE_HOLE: The input is a regular file. Holes will be converted |
| 60 | + * to "don't care" chunks. Other constant chunks will |
| 61 | + * be converted to fill chunks. |
| 62 | + */ |
| 63 | +enum sparse_read_mode { |
| 64 | + SPARSE_READ_MODE_NORMAL = false, |
| 65 | + SPARSE_READ_MODE_SPARSE = true, |
| 66 | + SPARSE_READ_MODE_HOLE, |
| 67 | +}; |
| 68 | + |
| 69 | /** |
| 70 | * sparse_file_read - read a file into a sparse file cookie |
| 71 | * |
| 72 | * @s - sparse file cookie |
| 73 | * @fd - file descriptor to read from |
| 74 | - * @sparse - read a file in the Android sparse file format |
| 75 | + * @mode - mode to use when reading the input file |
| 76 | * @crc - verify the crc of a file in the Android sparse file format |
| 77 | * |
| 78 | - * Reads a file into a sparse file cookie. If sparse is true, the file is |
| 79 | - * assumed to be in the Android sparse file format. If sparse is false, the |
| 80 | - * file will be sparsed by looking for block aligned chunks of all zeros or |
| 81 | - * another 32 bit value. If crc is true, the crc of the sparse file will be |
| 82 | - * verified. |
| 83 | + * Reads a file into a sparse file cookie. If @mode is |
| 84 | + * %SPARSE_READ_MODE_SPARSE, the file is assumed to be in the Android sparse |
| 85 | + * file format. If @mode is %SPARSE_READ_MODE_NORMAL, the file will be sparsed |
| 86 | + * by looking for block aligned chunks of all zeros or another 32 bit value. If |
| 87 | + * @mode is %SPARSE_READ_MODE_HOLE, the file will be sparsed like |
| 88 | + * %SPARSE_READ_MODE_NORMAL, but holes in the file will be converted to "don't |
| 89 | + * care" chunks. If crc is true, the crc of the sparse file will be verified. |
| 90 | * |
| 91 | * Returns 0 on success, negative errno on error. |
| 92 | */ |
| 93 | -int sparse_file_read(struct sparse_file *s, int fd, bool sparse, bool crc); |
| 94 | +int sparse_file_read(struct sparse_file *s, int fd, enum sparse_read_mode mode, bool crc); |
| 95 | |
| 96 | /** |
| 97 | * sparse_file_import - import an existing sparse file |
| 98 | diff --git a/libsparse/sparse_read.c b/libsparse/sparse_read.c |
| 99 | index ee4abd86a..81f48cc13 100644 |
| 100 | --- a/libsparse/sparse_read.c |
| 101 | +++ b/libsparse/sparse_read.c |
| 102 | @@ -414,16 +414,79 @@ static int sparse_file_read_normal(struct sparse_file* s, int fd) |
| 103 | return ret; |
| 104 | } |
| 105 | |
| 106 | -int sparse_file_read(struct sparse_file *s, int fd, bool sparse, bool crc) |
| 107 | +#ifdef __linux__ |
| 108 | +static int sparse_file_read_hole(struct sparse_file* s, int fd) |
| 109 | { |
| 110 | - if (crc && !sparse) { |
| 111 | + int ret; |
| 112 | + uint32_t* buf = (uint32_t*)malloc(s->block_size); |
| 113 | + int64_t end = 0; |
| 114 | + int64_t start = 0; |
| 115 | + |
| 116 | + if (!buf) { |
| 117 | + return -ENOMEM; |
| 118 | + } |
| 119 | + |
| 120 | + do { |
| 121 | + start = lseek(fd, end, SEEK_DATA); |
| 122 | + if (start < 0) { |
| 123 | + if (errno == ENXIO) |
| 124 | + /* The rest of the file is a hole */ |
| 125 | + break; |
| 126 | + |
| 127 | + error("could not seek to data"); |
| 128 | + free(buf); |
| 129 | + return -errno; |
| 130 | + } else if (start > s->len) { |
| 131 | + break; |
| 132 | + } |
| 133 | + |
| 134 | + end = lseek(fd, start, SEEK_HOLE); |
| 135 | + if (end < 0) { |
| 136 | + error("could not seek to end"); |
| 137 | + free(buf); |
| 138 | + return -errno; |
| 139 | + } |
| 140 | + end = min(end, s->len); |
| 141 | + |
| 142 | + start = ALIGN_DOWN(start, s->block_size); |
| 143 | + end = ALIGN(end, s->block_size); |
| 144 | + if (lseek(fd, start, SEEK_SET) < 0) { |
| 145 | + free(buf); |
| 146 | + return -errno; |
| 147 | + } |
| 148 | + |
| 149 | + ret = do_sparse_file_read_normal(s, fd, buf, start, end - start); |
| 150 | + if (ret) { |
| 151 | + free(buf); |
| 152 | + return ret; |
| 153 | + } |
| 154 | + } while (end < s->len); |
| 155 | + |
| 156 | + free(buf); |
| 157 | + return 0; |
| 158 | +} |
| 159 | +#else |
| 160 | +static int sparse_file_read_hole(struct sparse_file* s __unused, int fd __unused) |
| 161 | +{ |
| 162 | + return -ENOTSUP; |
| 163 | +} |
| 164 | +#endif |
| 165 | + |
| 166 | +int sparse_file_read(struct sparse_file *s, int fd, enum sparse_read_mode mode, bool crc) |
| 167 | +{ |
| 168 | + if (crc && mode != SPARSE_READ_MODE_SPARSE) { |
| 169 | return -EINVAL; |
| 170 | } |
| 171 | |
| 172 | - if (sparse) { |
| 173 | + switch (mode) { |
| 174 | + case SPARSE_READ_MODE_SPARSE: |
| 175 | return sparse_file_read_sparse(s, fd, crc); |
| 176 | - } else { |
| 177 | + case SPARSE_READ_MODE_NORMAL: |
| 178 | return sparse_file_read_normal(s, fd); |
| 179 | + case SPARSE_READ_MODE_HOLE: |
| 180 | + return sparse_file_read_hole(s, fd); |
| 181 | + default: |
| 182 | + return -EINVAL; |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | -- |
| 187 | 2.35.1.1320.gc452695387.dirty |
| 188 | |