Commit bc8e5f07 authored by Jan Kara's avatar Jan Kara
Browse files

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: default avatarJan Kara <jack@suse.cz>
parent 12755627

fs/quota/dquot.c

+26 −35
Original line number Diff line number Diff line
@@ -1703,16 +1703,19 @@ EXPORT_SYMBOL(dquot_free_inode); 


/*

 * 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 @@ static int __dquot_transfer(struct inode *inode, qid_t *chid, unsigned long mask 
	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 @@ static int __dquot_transfer(struct inode *inode, qid_t *chid, unsigned long mask 


	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;



	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);

	struct dquot *transfer_to[MAXQUOTAS] = {};

	struct super_block *sb = inode->i_sb;

	int ret;



	if (!sb_any_quota_active(sb) || IS_NOQUOTA(inode))

		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);

include/linux/quotaops.h

+1 −0
Original line number Diff line number Diff line
@@ -76,6 +76,7 @@ int vfs_get_dqblk(struct super_block *sb, int type, qid_t id, 
int vfs_set_dqblk(struct super_block *sb, int type, qid_t id,

		struct fs_disk_quota *di);



int __dquot_transfer(struct inode *inode, struct dquot **transfer_to);

int dquot_transfer(struct inode *inode, struct iattr *iattr);

int vfs_dq_quota_on_remount(struct super_block *sb);

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