against 2.6.12-rc4
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.
The patch was heavilly tested on 2.6.8 during 3 months,
this forward-ported version boots and works ok as well.
Signed-Off-By: Kirill Korotaev <[email protected]>
--- ./fs/fs-writeback.c.sbsync 2005-05-10 16:10:26.000000000 +0400
+++ ./fs/fs-writeback.c 2005-05-10 18:29:03.000000000 +0400
@@ -485,32 +485,6 @@ static void set_sb_syncing(int val)
spin_unlock(&sb_lock);
}
-/*
- * Find a superblock with inodes that need to be synced
- */
-static struct super_block *get_super_to_sync(void)
-{
- struct super_block *sb;
-restart:
- spin_lock(&sb_lock);
- sb = sb_entry(super_blocks.prev);
- for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
- if (sb->s_syncing)
- continue;
- sb->s_syncing = 1;
- 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;
-}
-
/**
* sync_inodes - writes all inodes to disk
* @wait: wait for completion
@@ -530,23 +504,39 @@ restart:
* outstanding dirty inodes, the writeback goes block-at-a-time within the
* filesystem's write_inode(). This is extremely slow.
*/
-void sync_inodes(int wait)
+static void __sync_inodes(int wait)
{
struct super_block *sb;
- set_sb_syncing(0);
- while ((sb = get_super_to_sync()) != NULL) {
- sync_inodes_sb(sb, 0);
- sync_blockdev(sb->s_bdev);
- drop_super(sb);
+ spin_lock(&sb_lock);
+restart:
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (sb->s_syncing)
+ continue;
+ sb->s_syncing = 1;
+ sb->s_count++;
+ spin_unlock(&sb_lock);
+ down_read(&sb->s_umount);
+ if (sb->s_root) {
+ sync_inodes_sb(sb, wait);
+ sync_blockdev(sb->s_bdev);
+ }
+ up_read(&sb->s_umount);
+ spin_lock(&sb_lock);
+ if (__put_super_and_need_restart(sb))
+ goto restart;
}
+ spin_unlock(&sb_lock);
+}
+
+void sync_inodes(int wait)
+{
+ set_sb_syncing(0);
+ __sync_inodes(0);
+
if (wait) {
set_sb_syncing(0);
- while ((sb = get_super_to_sync()) != NULL) {
- sync_inodes_sb(sb, 1);
- sync_blockdev(sb->s_bdev);
- drop_super(sb);
- }
+ __sync_inodes(1);
}
}
--- ./fs/quota.c.sbsync 2005-05-10 16:10:29.000000000 +0400
+++ ./fs/quota.c 2005-05-10 18:41:51.000000000 +0400
@@ -149,36 +149,6 @@ static int check_quotactl_valid(struct s
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_b
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 */
--- ./fs/super.c.sbsync 2005-05-10 17:53:36.000000000 +0400
+++ ./fs/super.c 2005-05-11 19:32:12.000000000 +0400
@@ -343,20 +343,22 @@ static inline void write_super(struct su
*/
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);
}
@@ -383,20 +385,16 @@ 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;
@@ -407,8 +405,11 @@ 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);
@@ -424,21 +425,25 @@ 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);
@@ -449,20 +454,22 @@ 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);
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