quota: Refactor dquot_transfer code so that OCFS2 can pass in its references
Currently, __dquot_transfer() acquires its own references of dquot structures
that will be put into inode. But for OCFS2, this creates a lock inversion
between dq_lock (waited on in dqget) and transaction start (started in
ocfs2_setattr). Currently, deadlock is impossible because dq_lock is acquired
only during dquot_acquire and dquot_release and we already hold a reference to
dquot structures in ocfs2_setattr so neither of these functions can be called
while we call dquot_transfer. But this is rather subtle and it is hard to teach
lockdep about it. So provide __dquot_transfer function that can be passed dquot
references directly. OCFS2 can then pass acquired dquot references directly to
__dquot_transfer with proper locking.
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 1056a21..655a4c5 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1703,16 +1703,19 @@
/*
* Transfer the number of inode and blocks from one diskquota to an other.
+ * On success, dquot references in transfer_to are consumed and references
+ * to original dquots that need to be released are placed there. On failure,
+ * references are kept untouched.
*
* This operation can block, but only after everything is updated
* A transaction must be started when entering this function.
+ *
*/
-static int __dquot_transfer(struct inode *inode, qid_t *chid, unsigned long mask)
+int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
{
qsize_t space, cur_space;
qsize_t rsv_space = 0;
- struct dquot *transfer_from[MAXQUOTAS];
- struct dquot *transfer_to[MAXQUOTAS];
+ struct dquot *transfer_from[MAXQUOTAS] = {};
int cnt, ret = 0;
char warntype_to[MAXQUOTAS];
char warntype_from_inodes[MAXQUOTAS], warntype_from_space[MAXQUOTAS];
@@ -1722,19 +1725,12 @@
if (IS_NOQUOTA(inode))
return 0;
/* Initialize the arrays */
- for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- transfer_from[cnt] = NULL;
- transfer_to[cnt] = NULL;
+ for (cnt = 0; cnt < MAXQUOTAS; cnt++)
warntype_to[cnt] = QUOTA_NL_NOWARN;
- }
- for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (mask & (1 << cnt))
- transfer_to[cnt] = dqget(inode->i_sb, chid[cnt], cnt);
- }
down_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
if (IS_NOQUOTA(inode)) { /* File without quota accounting? */
up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
- goto put_all;
+ return 0;
}
spin_lock(&dq_data_lock);
cur_space = inode_get_bytes(inode);
@@ -1786,46 +1782,41 @@
mark_all_dquot_dirty(transfer_from);
mark_all_dquot_dirty(transfer_to);
- /* The reference we got is transferred to the inode */
+ /* Pass back references to put */
for (cnt = 0; cnt < MAXQUOTAS; cnt++)
- transfer_to[cnt] = NULL;
-warn_put_all:
+ transfer_to[cnt] = transfer_from[cnt];
+warn:
flush_warnings(transfer_to, warntype_to);
flush_warnings(transfer_from, warntype_from_inodes);
flush_warnings(transfer_from, warntype_from_space);
-put_all:
- dqput_all(transfer_from);
- dqput_all(transfer_to);
return ret;
over_quota:
spin_unlock(&dq_data_lock);
up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
- /* Clear dquot pointers we don't want to dqput() */
- for (cnt = 0; cnt < MAXQUOTAS; cnt++)
- transfer_from[cnt] = NULL;
- goto warn_put_all;
+ goto warn;
}
+EXPORT_SYMBOL(__dquot_transfer);
/* Wrapper for transferring ownership of an inode for uid/gid only
* Called from FSXXX_setattr()
*/
int dquot_transfer(struct inode *inode, struct iattr *iattr)
{
- qid_t chid[MAXQUOTAS];
- unsigned long mask = 0;
+ struct dquot *transfer_to[MAXQUOTAS] = {};
+ struct super_block *sb = inode->i_sb;
+ int ret;
- if (iattr->ia_valid & ATTR_UID && iattr->ia_uid != inode->i_uid) {
- mask |= 1 << USRQUOTA;
- chid[USRQUOTA] = iattr->ia_uid;
- }
- if (iattr->ia_valid & ATTR_GID && iattr->ia_gid != inode->i_gid) {
- mask |= 1 << GRPQUOTA;
- chid[GRPQUOTA] = iattr->ia_gid;
- }
- if (sb_any_quota_active(inode->i_sb) && !IS_NOQUOTA(inode))
- return __dquot_transfer(inode, chid, mask);
+ if (!sb_any_quota_active(sb) || IS_NOQUOTA(inode))
+ return 0;
- return 0;
+ if (iattr->ia_valid & ATTR_UID && iattr->ia_uid != inode->i_uid)
+ transfer_to[USRQUOTA] = dqget(sb, iattr->ia_uid, USRQUOTA);
+ if (iattr->ia_valid & ATTR_GID && iattr->ia_gid != inode->i_gid)
+ transfer_to[GRPQUOTA] = dqget(sb, iattr->ia_uid, GRPQUOTA);
+
+ ret = __dquot_transfer(inode, transfer_to);
+ dqput_all(transfer_to);
+ return ret;
}
EXPORT_SYMBOL(dquot_transfer);
