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ocfs2: Fix quota locking

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OCFS2 had three issues with quota locking:
a) When reading dquot from global quota file, we started a transaction while
   holding dqio_mutex which is prone to deadlocks because other paths do it
   the other way around
b) During ocfs2_sync_dquot we were not protected against concurrent writers
   on the same node. Because we first copy data to local buffer, a race
   could happen resulting in old data being written to global quota file and
   thus causing quota inconsistency after a crash.
c) ip_alloc_sem of quota files was acquired while a transaction is started
   in ocfs2_quota_write which can deadlock because we first get ip_alloc_sem
   and then start a transaction when extending quota files.

We fix the problem a) by pulling all necessary code to ocfs2_acquire_dquot
and ocfs2_release_dquot. Thus we no longer depend on generic dquot_acquire
to do the locking and can force proper lock ordering.

Problems b) and c) are fixed by locking i_mutex and ip_alloc_sem of
global quota file in ocfs2_lock_global_qf and removing ip_alloc_sem from
ocfs2_quota_read and ocfs2_quota_write.

Acked-by: Joel Becker <Joel.Becker@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara
2010-03-31 16:25:37 +02:00
parent ae4f6ef134
commit fb8dd8d780
3 changed files with 214 additions and 186 deletions
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5
fs/ocfs2/quota.h
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@@ -104,10 +104,11 @@ static inline int ocfs2_global_release_dquot(struct dquot *dquot)
int ocfs2_lock_global_qf(struct ocfs2_mem_dqinfo *oinfo, int ex);
void ocfs2_unlock_global_qf(struct ocfs2_mem_dqinfo *oinfo, int ex);
int ocfs2_read_quota_block(struct inode *inode, u64 v_block,
struct buffer_head **bh);
int ocfs2_validate_quota_block(struct super_block *sb, struct buffer_head *bh);
int ocfs2_read_quota_phys_block(struct inode *inode, u64 p_block,
struct buffer_head **bh);
int ocfs2_create_local_dquot(struct dquot *dquot);
int ocfs2_local_release_dquot(handle_t *handle, struct dquot *dquot);
extern const struct dquot_operations ocfs2_quota_operations;
extern struct quota_format_type ocfs2_quota_format;