I had to update the 4k alignment patch for this. While it does apply, and the result compiles, and even appears to work fine superficially, I do not know if there have been any changes to squashfs internals that now require other places to take the alignment flag into account. Will do more testing soon.
99 lines
4 KiB
Diff
99 lines
4 KiB
Diff
This patch is an old patch; see below for the original message body. The patch
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has been updated twice: Once to apply to squashfs 4.4, commit
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52eb4c279cd283ed9802dd1ceb686560b22ffb67, and later to apply to squashfs 4.5,
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commit 0496d7c3de3e09da37ba492081c86159806ebb07.
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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 | 17 +++++++++++++++++
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1 file changed, 17 insertions(+)
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diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
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index aaa4b00..eb2fb23 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 nopad = FALSE;
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int exit_on_error = FALSE;
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long long start_offset = 0;
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int sleep_time = 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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@@ -1553,6 +1555,9 @@ 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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@@ -2460,6 +2465,9 @@ 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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@@ -2850,6 +2858,10 @@ 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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@@ -5975,6 +5987,7 @@ static void print_options(FILE *stream, char *name, int total_mem)
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fprintf(stream, "actions from <f>\n");
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fprintf(stream, "-false-action-file <f>\tas -false-action, but read ");
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fprintf(stream, "actions from <f>\n");
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+ fprintf(stream, "-4k-align\t\tenables 4k alignment of all files\n");
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fprintf(stream, "\nFilesystem filter options:\n");
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fprintf(stream, "-p <pseudo-definition>\tAdd pseudo file definition\n");
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fprintf(stream, "-pf <pseudo-file>\tAdd list of pseudo file definitions\n");
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@@ -6198,6 +6211,7 @@ 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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@@ -7499,6 +7513,9 @@ 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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print_version("mksquashfs");
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+
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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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2.32.0
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