Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=941d2380e979dfefb6c824452e9f42be3ef948ee
Commit: 941d2380e979dfefb6c824452e9f42be3ef948ee
Parent: bed9759b2e6bd938097389f6bd2ac8d622fa3884
Author: Jan Kara <[EMAIL PROTECTED]>
AuthorDate: Wed Feb 6 01:37:36 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Feb 6 10:41:07 2008 -0800
quota: improve inode list scanning in add_dquot_ref()
We restarted scan of sb->s_inodes list whenever we had to drop inode_lock
in add_dquot_ref(). This leads to overall quadratic running time and thus
add_dquot_ref() can take several minutes when called on a life filesystem.
We fix the problem by using the fact that inode cannot be removed from
s_inodes list while we hold a reference to it and thus we can safely
restart the scan if we don't drop the reference. Here we use the fact that
inodes freshly added to s_inodes list are already guaranteed to have quotas
properly initialized and the ordering of inodes on s_inodes list does not
change so we cannot skip any inode.
Thanks goes to Nick <[EMAIL PROTECTED]> for analyzing the problem and
testing the fix.
[EMAIL PROTECTED]: iput(NULL) is legal]
Signed-off-by: Jan Kara <[EMAIL PROTECTED]>
Cc: Nick <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
fs/dquot.c | 15 ++++++++++-----
1 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/fs/dquot.c b/fs/dquot.c
index cee7c6f..def4e96 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -696,9 +696,8 @@ static int dqinit_needed(struct inode *inode, int type)
/* This routine is guarded by dqonoff_mutex mutex */
static void add_dquot_ref(struct super_block *sb, int type)
{
- struct inode *inode;
+ struct inode *inode, *old_inode = NULL;
-restart:
spin_lock(&inode_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
if (!atomic_read(&inode->i_writecount))
@@ -711,12 +710,18 @@ restart:
__iget(inode);
spin_unlock(&inode_lock);
+ iput(old_inode);
sb->dq_op->initialize(inode, type);
- iput(inode);
- /* As we may have blocked we had better restart... */
- goto restart;
+ /* We hold a reference to 'inode' so it couldn't have been
+ * removed from s_inodes list while we dropped the inode_lock.
+ * We cannot iput the inode now as we can be holding the last
+ * reference and we cannot iput it under inode_lock. So we
+ * keep the reference and iput it later. */
+ old_inode = inode;
+ spin_lock(&inode_lock);
}
spin_unlock(&inode_lock);
+ iput(old_inode);
}
/* Return 0 if dqput() won't block (note that 1 doesn't necessarily mean
blocking) */
-
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