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authorJan Kara <jack@suse.cz>2017-06-08 17:09:46 +0300
committerJan Kara <jack@suse.cz>2017-08-17 20:03:16 +0300
commitd2faa415166b2883428efa92f451774ef44373ac (patch)
tree24e3f4fc0ef864c48f0751090937c09752657942
parent8fc32c2b0db2c9ee0dffebea65bcdea03a29ba5a (diff)
downloadlinux-d2faa415166b2883428efa92f451774ef44373ac.tar.xz
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 <adilger@dilger.ca> Signed-off-by: Jan Kara <jack@suse.cz>
-rw-r--r--fs/quota/quota_v2.c17
1 files changed, 14 insertions, 3 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;
-
- down_write(&dqopt->dqio_sem);
+ bool alloc = false;
+
+ /*
+ * 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;
}