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authorJan Kara <jack@suse.cz>2017-06-08 15:00:20 +0200
committerJan Kara <jack@suse.cz>2017-08-17 18:56:07 +0200
commit62676838cb39f4e4f44dd697c4d5d4214bda8cb1 (patch)
tree79460ae1e1a4703ab739915d6e821661d9493780
parentbc8230ee8e2ba967af780cdaf2dcc0f8e5eb45ca (diff)
downloadlinux-62676838cb39f4e4f44dd697c4d5d4214bda8cb1.tar.bz2
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>
-rw-r--r--fs/quota/dquot.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 29d447598642..21358f31923d 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -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;
}