quota: Allow negative usage of space and inodes

For clustered filesystems, it can happen that space / inode usage goes
negative temporarily (because some node is allocating another node
is freeing and they are not completely in sync). So let quota code
allow this and change qsize_t so a signed type so that we don't
underflow the variables.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

diff --git a/fs/dquot.c b/fs/dquot.c
index 74185c34a4f035998f15af2f8c53bd602545ffbe..9c78ffe1aad2e7408d92bc8460195e607e8ed0ce 100644 (file)
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -847,7 +847,8 @@ static inline void dquot_incr_space(struct dquot *dquot, qsize_t number)
 
 static inline void dquot_decr_inodes(struct dquot *dquot, qsize_t number)
 {
-       if (dquot->dq_dqb.dqb_curinodes > number)
+       if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NEGATIVE_USAGE ||
+           dquot->dq_dqb.dqb_curinodes >= number)
                dquot->dq_dqb.dqb_curinodes -= number;
        else
                dquot->dq_dqb.dqb_curinodes = 0;
@@ -858,7 +859,8 @@ static inline void dquot_decr_inodes(struct dquot *dquot, qsize_t number)
 
 static inline void dquot_decr_space(struct dquot *dquot, qsize_t number)
 {
-       if (dquot->dq_dqb.dqb_curspace > number)
+       if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NEGATIVE_USAGE ||
+           dquot->dq_dqb.dqb_curspace >= number)
                dquot->dq_dqb.dqb_curspace -= number;
        else
                dquot->dq_dqb.dqb_curspace = 0;

diff --git a/include/linux/quota.h b/include/linux/quota.h
index e51dfdc0aef008bc0ea1285185ecc481d319fac3..75bf761caef2f187b772b54bf8130560a95c9d42 100644 (file)
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -168,7 +168,7 @@ enum {
 #include <asm/atomic.h>
 
 typedef __kernel_uid32_t qid_t; /* Type in which we store ids in memory */
-typedef __u64 qsize_t;          /* Type in which we store sizes */
+typedef long long qsize_t;     /* Type in which we store sizes */
 
 extern spinlock_t dq_data_lock;
 
@@ -336,6 +336,7 @@ enum {
                                                 * responsible for setting
                                                 * S_NOQUOTA, S_NOATIME flags
                                                 */
+#define DQUOT_NEGATIVE_USAGE   (1 << 7)        /* Allow negative quota usage */
 
 static inline unsigned int dquot_state_flag(unsigned int flags, int type)
 {