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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>
This commit is contained in:
Jan Kara 2010-05-13 19:58:50 +02:00
parent 12755627bd
commit bc8e5f0739
2 changed files with 27 additions and 35 deletions
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61
fs/quota/dquot.c
View File

@ -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;
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);

1
include/linux/quotaops.h
View File

@ -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);