From: Kirill Korotaev <dev@sw.ru>
To: Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH] O(1) sb list traversing on syncs
Date: Wed, 11 May 2005 19:52:01 +0400 [thread overview]
Message-ID: <42822A21.8090600@sw.ru> (raw)
[-- Attachment #1: Type: text/plain, Size: 445 bytes --]
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 <dev@sw.ru>
[-- Attachment #2: diff-inode-sbsync-20050317-2 --]
[-- Type: text/plain, Size: 7597 bytes --]
--- ./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);
reply other threads:[~2005-05-11 15:53 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=42822A21.8090600@sw.ru \
--to=dev@sw.ru \
--cc=akpm@osdl.org \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@osdl.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.