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ext4: Use a hash of the topdir directory name for the Orlov parent group

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Instead of using a random number to determine the goal parent grop for
the Orlov top directories, use a hash of the directory name.  This
allows for repeatable results when trying to benchmark filesystem
layout algorithms.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2009-06-13 11:09:42 -04:00
parent 8a8a2050c8
commit f157a4aa98
4 changed files with 22 additions and 13 deletions
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3
fs/ext4/ext4.h
View File

@ -1315,7 +1315,8 @@ extern int ext4fs_dirhash(const char *name, int len, struct
dx_hash_info *hinfo);
/* ialloc.c */
extern struct inode * ext4_new_inode(handle_t *, struct inode *, int);
extern struct inode *ext4_new_inode(handle_t *, struct inode *, int,
const struct qstr *qstr);
extern void ext4_free_inode(handle_t *, struct inode *);
extern struct inode * ext4_orphan_get(struct super_block *, unsigned long);
extern unsigned long ext4_count_free_inodes(struct super_block *);

19
fs/ext4/ialloc.c
View File

@ -470,7 +470,8 @@ void get_orlov_stats(struct super_block *sb, ext4_group_t g,
*/
static int find_group_orlov(struct super_block *sb, struct inode *parent,
ext4_group_t *group, int mode)
ext4_group_t *group, int mode,
const struct qstr *qstr)
{
ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
struct ext4_sb_info *sbi = EXT4_SB(sb);
@ -485,6 +486,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
struct ext4_group_desc *desc;
struct orlov_stats stats;
int flex_size = ext4_flex_bg_size(sbi);
struct dx_hash_info hinfo;
ngroups = real_ngroups;
if (flex_size > 1) {
@ -506,7 +508,13 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
int best_ndir = inodes_per_group;
int ret = -1;
get_random_bytes(&grp, sizeof(grp));
if (qstr) {
hinfo.hash_version = DX_HASH_HALF_MD4;
hinfo.seed = sbi->s_hash_seed;
ext4fs_dirhash(qstr->name, qstr->len, &hinfo);
grp = hinfo.hash;
} else
get_random_bytes(&grp, sizeof(grp));
parent_group = (unsigned)grp % ngroups;
for (i = 0; i < ngroups; i++) {
g = (parent_group + i) % ngroups;
@ -649,7 +657,7 @@ static int find_group_other(struct super_block *sb, struct inode *parent,
*group = parent_group + flex_size;
if (*group > ngroups)
*group = 0;
return find_group_orlov(sb, parent, group, mode);
return find_group_orlov(sb, parent, group, mode, 0);
}
/*
@ -790,7 +798,8 @@ err_ret:
* For other inodes, search forward from the parent directory's block
* group to find a free inode.
*/
struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
const struct qstr *qstr)
{
struct super_block *sb;
struct buffer_head *inode_bitmap_bh = NULL;
@ -839,7 +848,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
if (test_opt(sb, OLDALLOC))
ret2 = find_group_dir(sb, dir, &group);
else
ret2 = find_group_orlov(sb, dir, &group, mode);
ret2 = find_group_orlov(sb, dir, &group, mode, qstr);
} else
ret2 = find_group_other(sb, dir, &group, mode);

5
fs/ext4/migrate.c
View File

@ -483,9 +483,8 @@ int ext4_ext_migrate(struct inode *inode)
retval = PTR_ERR(handle);
return retval;
}
tmp_inode = ext4_new_inode(handle,
inode->i_sb->s_root->d_inode,
S_IFREG);
tmp_inode = ext4_new_inode(handle, inode->i_sb->s_root->d_inode,
S_IFREG, 0);
if (IS_ERR(tmp_inode)) {
retval = -ENOMEM;
ext4_journal_stop(handle);

8
fs/ext4/namei.c
View File

@ -1782,7 +1782,7 @@ retry:
if (IS_DIRSYNC(dir))
ext4_handle_sync(handle);
inode = ext4_new_inode (handle, dir, mode);
inode = ext4_new_inode(handle, dir, mode, &dentry->d_name);
err = PTR_ERR(inode);
if (!IS_ERR(inode)) {
inode->i_op = &ext4_file_inode_operations;
@ -1816,7 +1816,7 @@ retry:
if (IS_DIRSYNC(dir))
ext4_handle_sync(handle);
inode = ext4_new_inode(handle, dir, mode);
inode = ext4_new_inode(handle, dir, mode, &dentry->d_name);
err = PTR_ERR(inode);
if (!IS_ERR(inode)) {
init_special_inode(inode, inode->i_mode, rdev);
@ -1853,7 +1853,7 @@ retry:
if (IS_DIRSYNC(dir))
ext4_handle_sync(handle);
inode = ext4_new_inode(handle, dir, S_IFDIR | mode);
inode = ext4_new_inode(handle, dir, S_IFDIR | mode, &dentry->d_name);
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out_stop;
@ -2264,7 +2264,7 @@ retry:
if (IS_DIRSYNC(dir))
ext4_handle_sync(handle);
inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO);
inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO, &dentry->d_name);
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out_stop;