Commit 62676838 authored by Jan Kara's avatar Jan Kara
Browse files

quota: Do more fine-grained locking in dquot_acquire() 



We need dqio_sem held just for reading when calling ->read_dqblk() in
dquot_acquire(). Also dqio_sem is not needed when setting DQ_READ_B and
DQ_ACTIVE_B as concurrent reads and dquot activations are serialized by
dq_lock. So acquire and release dqio_sem closer to the place where it is
needed. This reduces lock hold time and will make locking changes
easier.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent bc8230ee

fs/quota/dquot.c

+6 −3
Original line number Diff line number Diff line
@@ -406,9 +406,11 @@ int dquot_acquire(struct dquot *dquot) 
	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);



	mutex_lock(&dquot->dq_lock);

	down_write(&dqopt->dqio_sem);

	if (!test_bit(DQ_READ_B, &dquot->dq_flags))

	if (!test_bit(DQ_READ_B, &dquot->dq_flags)) {

		down_read(&dqopt->dqio_sem);

		ret = dqopt->ops[dquot->dq_id.type]->read_dqblk(dquot);

		up_read(&dqopt->dqio_sem);

	}

	if (ret < 0)

		goto out_iolock;

	/* Make sure flags update is visible after dquot has been filled */
@@ -416,12 +418,14 @@ int dquot_acquire(struct dquot *dquot) 
	set_bit(DQ_READ_B, &dquot->dq_flags);

	/* Instantiate dquot if needed */

	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags) && !dquot->dq_off) {

		down_write(&dqopt->dqio_sem);

		ret = dqopt->ops[dquot->dq_id.type]->commit_dqblk(dquot);

		/* Write the info if needed */

		if (info_dirty(&dqopt->info[dquot->dq_id.type])) {

			ret2 = dqopt->ops[dquot->dq_id.type]->write_file_info(

					dquot->dq_sb, dquot->dq_id.type);

		}

		up_write(&dqopt->dqio_sem);

		if (ret < 0)

			goto out_iolock;

		if (ret2 < 0) {
@@ -436,7 +440,6 @@ int dquot_acquire(struct dquot *dquot) 
	smp_mb__before_atomic();

	set_bit(DQ_ACTIVE_B, &dquot->dq_flags);

out_iolock:

	up_write(&dqopt->dqio_sem);

	mutex_unlock(&dquot->dq_lock);

	return ret;

}

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