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authorJan Kara <jack@suse.cz>2008-02-06 01:37:36 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-06 10:41:07 -0800
commit941d2380e979dfefb6c824452e9f42be3ef948ee (patch)
tree4aad1ad817fb2043b8191ef77ec96845b9c24313
parentbed9759b2e6bd938097389f6bd2ac8d622fa3884 (diff)
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 <gentuu@gmail.com> for analyzing the problem and testing the fix. [akpm@linux-foundation.org: iput(NULL) is legal] Signed-off-by: Jan Kara <jack@suse.cz> Cc: Nick <gentuu@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/dquot.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/fs/dquot.c b/fs/dquot.c
index cee7c6f428f..def4e969df7 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) */