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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: Jan Kara <jack@suse.cz>
zero-colors
Jan Kara 2017-06-08 15:00:20 +02:00
parent bc8230ee8e
commit 62676838cb
1 changed files with 6 additions and 3 deletions
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9
fs/quota/dquot.c
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@ -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;
}