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/*
* 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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