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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 <dev@sw.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Kirill Korotaev
2005-06-23 00:09:54 -07:00
committed by Linus Torvalds
parent 4fea2838aa
commit 618f06362a
3 changed files with 96 additions and 111 deletions
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60
fs/quota.c
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@@ -149,36 +149,6 @@ static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t
return error;
}
static struct super_block *get_super_to_sync(int type)
{
struct list_head *head;
int cnt, dirty;
restart:
spin_lock(&sb_lock);
list_for_each(head, &super_blocks) {
struct super_block *sb = list_entry(head, struct super_block, s_list);
/* This test just improves performance so it needn't be reliable... */
for (cnt = 0, dirty = 0; cnt < MAXQUOTAS; cnt++)
if ((type == cnt || type == -1) && sb_has_quota_enabled(sb, cnt)
&& info_any_dirty(&sb_dqopt(sb)->info[cnt]))
dirty = 1;
if (!dirty)
continue;
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (!sb->s_root) {
drop_super(sb);
goto restart;
}
return sb;
}
spin_unlock(&sb_lock);
return NULL;
}
static void quota_sync_sb(struct super_block *sb, int type)
{
int cnt;
@@ -219,17 +189,35 @@ static void quota_sync_sb(struct super_block *sb, int type)
void sync_dquots(struct super_block *sb, int type)
{
int cnt, dirty;
if (sb) {
if (sb->s_qcop->quota_sync)
quota_sync_sb(sb, type);
return;
}
else {
while ((sb = get_super_to_sync(type)) != NULL) {
if (sb->s_qcop->quota_sync)
quota_sync_sb(sb, type);
drop_super(sb);
}
spin_lock(&sb_lock);
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
/* This test just improves performance so it needn't be reliable... */
for (cnt = 0, dirty = 0; cnt < MAXQUOTAS; cnt++)
if ((type == cnt || type == -1) && sb_has_quota_enabled(sb, cnt)
&& info_any_dirty(&sb_dqopt(sb)->info[cnt]))
dirty = 1;
if (!dirty)
continue;
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root && sb->s_qcop->quota_sync)
quota_sync_sb(sb, type);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
spin_unlock(&sb_lock);
}
/* Copy parameters and call proper function */