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[PATCH] O(1) sb list traversing on syncs

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This patch removes O(n^2) super block loops in sync_inodes(),
sync_filesystems() etc.  in favour of using __put_super_and_need_restart()
which I introduced earlier.  We faced a noticably long freezes on sb
syncing when there are thousands of super blocks in the system.

Signed-Off-By: Kirill Korotaev <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Kirill Korotaev 2005-06-23 00:09:54 -07:00 • committed by Linus Torvalds
commit 618f06362a
3 changed files with 96 additions and 111 deletions
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83
fs/super.c
View file

@ -341,20 +341,22 @@ static inline void write_super(struct super_block *sb)
*/
void sync_supers(void)
{
struct super_block * sb;
restart:
struct super_block *sb;
spin_lock(&sb_lock);
sb = sb_entry(super_blocks.next);
while (sb != sb_entry(&super_blocks))
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_dirt) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
write_super(sb);
drop_super(sb);
goto restart;
} else
sb = sb_entry(sb->s_list.next);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
}
spin_unlock(&sb_lock);
}
@ -381,20 +383,16 @@ void sync_filesystems(int wait)
down(&mutex); /* Could be down_interruptible */
spin_lock(&sb_lock);
for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
sb = sb_entry(sb->s_list.next)) {
list_for_each_entry(sb, &super_blocks, s_list) {
if (!sb->s_op->sync_fs)
continue;
if (sb->s_flags & MS_RDONLY)
continue;
sb->s_need_sync_fs = 1;
}
spin_unlock(&sb_lock);
restart:
spin_lock(&sb_lock);
for (sb = sb_entry(super_blocks.next); sb != sb_entry(&super_blocks);
sb = sb_entry(sb->s_list.next)) {
list_for_each_entry(sb, &super_blocks, s_list) {
if (!sb->s_need_sync_fs)
continue;
sb->s_need_sync_fs = 0;
@ -405,8 +403,11 @@ restart:
down_read(&sb->s_umount);
if (sb->s_root && (wait || sb->s_dirt))
sb->s_op->sync_fs(sb, wait);
drop_super(sb);
goto restart;
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
spin_unlock(&sb_lock);
up(&mutex);
@ -422,21 +423,25 @@ restart:
struct super_block * get_super(struct block_device *bdev)
{
struct list_head *p;
struct super_block *sb;
if (!bdev)
return NULL;
rescan:
spin_lock(&sb_lock);
list_for_each(p, &super_blocks) {
struct super_block *s = sb_entry(p);
if (s->s_bdev == bdev) {
s->s_count++;
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_bdev == bdev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&s->s_umount);
if (s->s_root)
return s;
drop_super(s);
goto rescan;
down_read(&sb->s_umount);
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto rescan;
}
}
spin_unlock(&sb_lock);
@ -447,20 +452,22 @@ EXPORT_SYMBOL(get_super);
struct super_block * user_get_super(dev_t dev)
{
struct list_head *p;
struct super_block *sb;
rescan:
spin_lock(&sb_lock);
list_for_each(p, &super_blocks) {
struct super_block *s = sb_entry(p);
if (s->s_dev == dev) {
s->s_count++;
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_dev == dev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&s->s_umount);
if (s->s_root)
return s;
drop_super(s);
goto rescan;
down_read(&sb->s_umount);
if (sb->s_root)
return sb;
up_read(&sb->s_umount);
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto rescan;
}
}
spin_unlock(&sb_lock);