100 lines
4.2 KiB
Diff
100 lines
4.2 KiB
Diff
This patch is an old patch; see below for the original message body. The patch
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has been updated several times to be compatible with new releases.
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* To apply to squashfs 4.4, commit 52eb4c279cd283ed9802dd1ceb686560b22ffb67.
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* To apply to squashfs 4.5, commit 0496d7c3de3e09da37ba492081c86159806ebb07.
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* To apply to squashfs 4.6, commit f7623b3d9953a1190fec181708c9489ef3522b9f.
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From af8a6dca694ddd38d8a775a2b5f9a24fe2d10153 Mon Sep 17 00:00:00 2001
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From: Amin Hassani <ahassani@google.com>
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Date: Thu, 15 Dec 2016 10:43:15 -0800
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Subject: [PATCH] mksquashfs 4K aligns the files inside the squashfs image
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Files inside a squashfs image are not necessarily 4k (4096)
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aligned. This patch starts each file in a 4k aligned address and pads
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zero to the end of the file until it reaches the next 4k aligned
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address. This will not change the size of the compressed
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blocks (especially the last one) and hence it will not change how the
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files are being loaded in kernel or unsquashfs. However on average this
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increases the size of the squashfs image which can be calculated by the
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following formula:
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increased_size = (number_of_unfragmented_files_in_image + number of fragments) * 2048
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The 4k alignment can be enabled by flag '-4k-align'
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---
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squashfs-tools/mksquashfs.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
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index 3429aac..db164c2 100644
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--- a/squashfs-tools/mksquashfs.c
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+++ b/squashfs-tools/mksquashfs.c
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@@ -82,6 +82,8 @@ int noI = FALSE;
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int noId = FALSE;
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int noD = FALSE;
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int noX = FALSE;
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+int do_4k_align = FALSE;
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+#define ALIGN_UP(bytes, size) (bytes = (bytes + size - 1) & ~(size - 1))
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/* block size used to build filesystem */
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int block_size = SQUASHFS_FILE_SIZE;
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@@ -1624,6 +1626,9 @@ static void unlock_fragments()
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* queue at this time.
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*/
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while(!queue_empty(locked_fragment)) {
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+ // 4k align the start of remaining queued fragments.
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+ if(do_4k_align)
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+ ALIGN_UP(bytes, 4096);
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write_buffer = queue_get(locked_fragment);
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frg = write_buffer->block;
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size = SQUASHFS_COMPRESSED_SIZE_BLOCK(fragment_table[frg].size);
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@@ -2627,6 +2632,9 @@ static void *frag_deflator(void *arg)
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write_buffer->size = compressed_size;
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pthread_mutex_lock(&fragment_mutex);
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if(fragments_locked == FALSE) {
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+ // 4k align the start of each fragment.
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+ if(do_4k_align)
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+ ALIGN_UP(bytes, 4096);
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fragment_table[file_buffer->block].size = c_byte;
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fragment_table[file_buffer->block].start_block = bytes;
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write_buffer->block = bytes;
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@@ -3021,6 +3029,10 @@ static struct file_info *write_file_blocks(int *status, struct dir_ent *dir_ent,
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struct file_info *file;
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int bl_hash = 0;
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+ // 4k align the start of each file.
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+ if(do_4k_align)
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+ ALIGN_UP(bytes, 4096);
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+
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if(pre_duplicate(read_size, dir_ent->inode, read_buffer, &bl_hash))
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return write_file_blocks_dup(status, dir_ent, read_buffer, dup, bl_hash);
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@@ -6169,6 +6181,7 @@ static void print_options(FILE *stream, char *name, int total_mem)
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fprintf(stream, "or metadata. This is\n\t\t\tequivalent to ");
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fprintf(stream, "specifying -noI -noD -noF and -noX\n");
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fprintf(stream, "\nFilesystem build options:\n");
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+ fprintf(stream, "-4k-align\t\tenables 4k alignment of all files\n");
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fprintf(stream, "-tar\t\t\tread uncompressed tar file from standard in (stdin)\n");
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fprintf(stream, "-no-strip\t\tact like tar, and do not strip leading ");
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fprintf(stream, "directories\n\t\t\tfrom source files\n");
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@@ -6690,6 +6703,7 @@ static void print_summary()
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"compressed", no_fragments ? "no" : noF ? "uncompressed" :
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"compressed", no_xattrs ? "no" : noX ? "uncompressed" :
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"compressed", noI || noId ? "uncompressed" : "compressed");
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+ printf("\t4k %saligned\n", do_4k_align ? "" : "un");
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printf("\tduplicates are %sremoved\n", duplicate_checking ? "" :
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"not ");
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printf("Filesystem size %.2f Kbytes (%.2f Mbytes)\n", bytes / 1024.0,
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@@ -8417,6 +8431,8 @@ print_compressor_options:
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} else if(strcmp(argv[i], "-comp") == 0) {
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/* parsed previously */
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i++;
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+ } else if(strcmp(argv[i], "-4k-align") == 0) {
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+ do_4k_align = TRUE;
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} else {
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ERROR("%s: invalid option\n\n", argv[0]);
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print_options(stderr, argv[0], total_mem);
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--
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2.39.2
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