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-rw-r--r--e2fsck/readahead.c254
1 files changed, 254 insertions, 0 deletions
diff --git a/e2fsck/readahead.c b/e2fsck/readahead.c
new file mode 100644
index 0000000..38d4ec4
--- /dev/null
+++ b/e2fsck/readahead.c
@@ -0,0 +1,254 @@
+/*
+ * readahead.c -- Prefetch filesystem metadata to speed up fsck.
+ *
+ * Copyright (C) 2014 Oracle.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#include "config.h"
+#include <string.h>
+
+#include "e2fsck.h"
+
+#undef DEBUG
+
+#ifdef DEBUG
+# define dbg_printf(f, a...) do {printf(f, ## a); fflush(stdout); } while (0)
+#else
+# define dbg_printf(f, a...)
+#endif
+
+struct read_dblist {
+ errcode_t err;
+ blk64_t run_start;
+ blk64_t run_len;
+ int flags;
+};
+
+static int readahead_dir_block(ext2_filsys fs, struct ext2_db_entry2 *db,
+ void *priv_data)
+{
+ struct read_dblist *pr = priv_data;
+ e2_blkcnt_t count = (pr->flags & E2FSCK_RA_DBLIST_IGNORE_BLOCKCNT ?
+ 1 : db->blockcnt);
+
+ if (!pr->run_len || db->blk != pr->run_start + pr->run_len) {
+ if (pr->run_len) {
+ pr->err = io_channel_cache_readahead(fs->io,
+ pr->run_start,
+ pr->run_len);
+ dbg_printf("readahead start=%llu len=%llu err=%d\n",
+ pr->run_start, pr->run_len,
+ (int)pr->err);
+ }
+ pr->run_start = db->blk;
+ pr->run_len = 0;
+ }
+ pr->run_len += count;
+
+ return pr->err ? DBLIST_ABORT : 0;
+}
+
+errcode_t e2fsck_readahead_dblist(ext2_filsys fs, int flags,
+ ext2_dblist dblist,
+ unsigned long long start,
+ unsigned long long count)
+{
+ errcode_t err;
+ struct read_dblist pr;
+
+ dbg_printf("%s: flags=0x%x\n", __func__, flags);
+ if (flags & ~E2FSCK_RA_DBLIST_ALL_FLAGS)
+ return EXT2_ET_INVALID_ARGUMENT;
+
+ memset(&pr, 0, sizeof(pr));
+ pr.flags = flags;
+ err = ext2fs_dblist_iterate3(dblist, readahead_dir_block, start,
+ count, &pr);
+ if (pr.err)
+ return pr.err;
+ if (err)
+ return err;
+
+ if (pr.run_len)
+ err = io_channel_cache_readahead(fs->io, pr.run_start,
+ pr.run_len);
+
+ return err;
+}
+
+static errcode_t e2fsck_readahead_bitmap(ext2_filsys fs,
+ ext2fs_block_bitmap ra_map)
+{
+ blk64_t start, end, out;
+ errcode_t err;
+
+ start = 1;
+ end = ext2fs_blocks_count(fs->super) - 1;
+
+ err = ext2fs_find_first_set_block_bitmap2(ra_map, start, end, &out);
+ while (err == 0) {
+ start = out;
+ err = ext2fs_find_first_zero_block_bitmap2(ra_map, start, end,
+ &out);
+ if (err == ENOENT) {
+ out = end;
+ err = 0;
+ if (out == start)
+ break;
+ } else if (err)
+ break;
+
+ err = io_channel_cache_readahead(fs->io, start, out - start);
+ if (err)
+ break;
+ start = out;
+ err = ext2fs_find_first_set_block_bitmap2(ra_map, start, end,
+ &out);
+ }
+
+ if (err == ENOENT)
+ err = 0;
+
+ return err;
+}
+
+/* Try not to spew bitmap range errors for readahead */
+static errcode_t mark_bmap_range(ext2fs_block_bitmap map,
+ blk64_t blk, unsigned int num)
+{
+ if (blk >= ext2fs_get_generic_bmap_start(map) &&
+ blk + num <= ext2fs_get_generic_bmap_end(map))
+ ext2fs_mark_block_bitmap_range2(map, blk, num);
+ else
+ return EXT2_ET_INVALID_ARGUMENT;
+ return 0;
+}
+
+static errcode_t mark_bmap(ext2fs_block_bitmap map, blk64_t blk)
+{
+ if (blk >= ext2fs_get_generic_bmap_start(map) &&
+ blk <= ext2fs_get_generic_bmap_end(map))
+ ext2fs_mark_block_bitmap2(map, blk);
+ else
+ return EXT2_ET_INVALID_ARGUMENT;
+ return 0;
+}
+
+errcode_t e2fsck_readahead(ext2_filsys fs, int flags, dgrp_t start,
+ dgrp_t ngroups)
+{
+ blk64_t super, old_gdt, new_gdt;
+ blk_t blocks;
+ dgrp_t i;
+ ext2fs_block_bitmap ra_map = NULL;
+ dgrp_t end = start + ngroups;
+ errcode_t err = 0;
+
+ dbg_printf("%s: flags=0x%x start=%d groups=%d\n", __func__, flags,
+ start, ngroups);
+ if (flags & ~E2FSCK_READA_ALL_FLAGS)
+ return EXT2_ET_INVALID_ARGUMENT;
+
+ if (end > fs->group_desc_count)
+ end = fs->group_desc_count;
+
+ if (flags == 0)
+ return 0;
+
+ err = ext2fs_allocate_block_bitmap(fs, "readahead bitmap",
+ &ra_map);
+ if (err)
+ return err;
+
+ for (i = start; i < end; i++) {
+ err = ext2fs_super_and_bgd_loc2(fs, i, &super, &old_gdt,
+ &new_gdt, &blocks);
+ if (err)
+ break;
+
+ if (flags & E2FSCK_READA_SUPER) {
+ err = mark_bmap(ra_map, super);
+ if (err)
+ break;
+ }
+
+ if (flags & E2FSCK_READA_GDT) {
+ err = mark_bmap_range(ra_map,
+ old_gdt ? old_gdt : new_gdt,
+ blocks);
+ if (err)
+ break;
+ }
+
+ if ((flags & E2FSCK_READA_BBITMAP) &&
+ !ext2fs_bg_flags_test(fs, i, EXT2_BG_BLOCK_UNINIT) &&
+ ext2fs_bg_free_blocks_count(fs, i) <
+ fs->super->s_blocks_per_group) {
+ super = ext2fs_block_bitmap_loc(fs, i);
+ err = mark_bmap(ra_map, super);
+ if (err)
+ break;
+ }
+
+ if ((flags & E2FSCK_READA_IBITMAP) &&
+ !ext2fs_bg_flags_test(fs, i, EXT2_BG_INODE_UNINIT) &&
+ ext2fs_bg_free_inodes_count(fs, i) <
+ fs->super->s_inodes_per_group) {
+ super = ext2fs_inode_bitmap_loc(fs, i);
+ err = mark_bmap(ra_map, super);
+ if (err)
+ break;
+ }
+
+ if ((flags & E2FSCK_READA_ITABLE) &&
+ ext2fs_bg_free_inodes_count(fs, i) <
+ fs->super->s_inodes_per_group) {
+ super = ext2fs_inode_table_loc(fs, i);
+ blocks = fs->inode_blocks_per_group -
+ (ext2fs_bg_itable_unused(fs, i) *
+ EXT2_INODE_SIZE(fs->super) / fs->blocksize);
+ err = mark_bmap_range(ra_map, super, blocks);
+ if (err)
+ break;
+ }
+ }
+
+ if (!err)
+ err = e2fsck_readahead_bitmap(fs, ra_map);
+
+ ext2fs_free_block_bitmap(ra_map);
+ return err;
+}
+
+int e2fsck_can_readahead(ext2_filsys fs)
+{
+ errcode_t err;
+
+ err = io_channel_cache_readahead(fs->io, 0, 1);
+ dbg_printf("%s: supp=%d\n", __func__, err != EXT2_ET_OP_NOT_SUPPORTED);
+ return err != EXT2_ET_OP_NOT_SUPPORTED;
+}
+
+unsigned long long e2fsck_guess_readahead(ext2_filsys fs)
+{
+ unsigned long long guess;
+
+ /*
+ * The optimal readahead sizes were experimentally determined by
+ * djwong in August 2014. Setting the RA size to two block groups'
+ * worth of inode table blocks seems to yield the largest reductions
+ * in e2fsck runtime.
+ */
+ guess = 2ULL * fs->blocksize * fs->inode_blocks_per_group;
+
+ /* Disable RA if it'd use more 1/50th of RAM. */
+ if (get_memory_size() > (guess * 50))
+ return guess / 1024;
+
+ return 0;
+}
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