93 lines
3.6 KiB
Diff
93 lines
3.6 KiB
Diff
From 7bda7c75748f36b0a50f93e46144d5a4de4974ad 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 8b1376f..683973d 100644
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--- a/squashfs-tools/mksquashfs.c
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+++ b/squashfs-tools/mksquashfs.c
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@@ -99,6 +99,8 @@ int old_exclude = TRUE;
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int use_regex = FALSE;
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int nopad = FALSE;
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int exit_on_error = FALSE;
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static off_t squashfs_start_offset = 0;
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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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long long global_uid = -1, global_gid = -1;
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@@ -1513,6 +1515,9 @@ 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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@@ -2420,6 +2420,9 @@
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compressed_size = SQUASHFS_COMPRESSED_SIZE_BLOCK(c_byte);
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write_buffer->size = compressed_size;
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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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@@ -2761,6 +2769,10 @@ int write_file_blocks(squashfs_inode *inode, struct dir_ent *dir_ent,
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long long sparse = 0;
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struct file_buffer *fragment_buffer = NULL;
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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))
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return write_file_blocks_dup(inode, dir_ent, read_buffer, dup);
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@@ -4692,6 +4704,7 @@ void write_filesystem_tables(struct squashfs_super_block *sBlk, int nopad)
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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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@@ -5346,6 +5359,8 @@ print_compressor_options:
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root_name = argv[i];
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} else if(strcmp(argv[i], "-version") == 0) {
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VERSION();
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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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printOptions:
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@@ -5387,6 +5402,7 @@ printOptions:
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ERROR("\t\t\tdirectory containing that directory, "
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"rather than the\n");
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ERROR("\t\t\tcontents of the directory\n");
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+ ERROR("-4k-align\t\tenables 4k alignment of all files\n");
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ERROR("\nFilesystem filter options:\n");
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ERROR("-p <pseudo-definition>\tAdd pseudo file "
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"definition\n");
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--
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2.14.1.480.gb18f417b89-goog (previously; hand-patched by charles-dyfis-net)
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