From d2faa415166b2883428efa92f451774ef44373ac Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 8 Jun 2017 16:09:46 +0200 Subject: [PATCH] quota: Do not acquire dqio_sem for dquot overwrites in v2 format When dquot has space already allocated in a quota file, we just overwrite that place when writing dquot. So we don't need any protection against other modifications of quota file as these keep dquot in place. Reviewed-by: Andreas Dilger Signed-off-by: Jan Kara --- fs/quota/quota_v2.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/quota/quota_v2.c b/fs/quota/quota_v2.c index 482733abe4ac..7a05b80f3b8c 100644 --- a/fs/quota/quota_v2.c +++ b/fs/quota/quota_v2.c @@ -300,12 +300,23 @@ static int v2_write_dquot(struct dquot *dquot) { struct quota_info *dqopt = sb_dqopt(dquot->dq_sb); int ret; + bool alloc = false; - down_write(&dqopt->dqio_sem); + /* + * If space for dquot is already allocated, we don't need any + * protection as we'll only overwrite the place of dquot. We are + * still protected by concurrent writes of the same dquot by + * dquot->dq_lock. + */ + if (!dquot->dq_off) { + alloc = true; + down_write(&dqopt->dqio_sem); + } ret = qtree_write_dquot( sb_dqinfo(dquot->dq_sb, dquot->dq_id.type)->dqi_priv, dquot); - up_write(&dqopt->dqio_sem); + if (alloc) + up_write(&dqopt->dqio_sem); return ret; }