redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

quota: Protect dquot writeout with dq_lock 

Currently dquot writeout is only protected by dqio_sem held for writing.
As we transition to a finer grained locking we will use dquot->dq_lock
instead. So acquire it in dquot_commit() and move dqio_sem just around
->commit_dqblk() call as it is still needed to serialize quota file
changes.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Jan Kara <jack@suse.cz>
hifive-unleashed-5.1
Jan Kara 2017-06-08 15:16:41 +02:00
parent d6ab366102
commit 5e8cb9b624
1 changed files with 14 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
fs/quota/dquot.c
View File

@ -110,14 +110,11 @@
* sure they cannot race with quotaon which first sets S_NOQUOTA flag and
* then drops all pointers to dquots from an inode.
*
* Each dquot has its dq_lock mutex. Locked dquots might not be referenced
* from inodes (dquot_alloc_space() and such don't check the dq_lock).
* Currently dquot is locked only when it is being read to memory (or space for
* it is being allocated) on the first dqget() and when it is being released on
* the last dqput(). The allocation and release oparations are serialized by
* the dq_lock and by checking the use count in dquot_release(). Write
* operations on dquots don't hold dq_lock as they copy data under dq_data_lock
* spinlock to internal buffers before writing.
* Each dquot has its dq_lock mutex. Dquot is locked when it is being read to
* memory (or space for it is being allocated) on the first dqget(), when it is
* being written out, and when it is being released on the last dqput(). The
* allocation and release operations are serialized by the dq_lock and by
* checking the use count in dquot_release().
*
* Lock ordering (including related VFS locks) is the following:
* s_umount > i_mutex > journal_lock > dquot->dq_lock > dqio_sem
@ -453,21 +450,24 @@ int dquot_commit(struct dquot *dquot)
int ret = 0;
struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
down_write(&dqopt->dqio_sem);
mutex_lock(&dquot->dq_lock);
spin_lock(&dq_list_lock);
if (!clear_dquot_dirty(dquot)) {
spin_unlock(&dq_list_lock);
goto out_sem;
goto out_lock;
}
spin_unlock(&dq_list_lock);
/* Inactive dquot can be only if there was error during read/init
* => we have better not writing it */
if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
down_write(&dqopt->dqio_sem);
ret = dqopt->ops[dquot->dq_id.type]->commit_dqblk(dquot);
else
up_write(&dqopt->dqio_sem);
} else {
ret = -EIO;
out_sem:
up_write(&dqopt->dqio_sem);
}
out_lock:
mutex_unlock(&dquot->dq_lock);
return ret;
}
EXPORT_SYMBOL(dquot_commit);