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SubjectRe: sync problem in 2.2.5
  Hello.

> Worked!!!
>
> All I did is to remove the /quota* files and then quotaoff -a
>
> No more problems... so far
>
> I have tryied what normally locks up systematicaly the sync command.
> While heavy Disk IO doing a sync and no more problems.
>
> So I really, so far, suspect problems in the quota code in the kernel.
>
> Can somebody verify that and confirm my problem?
I've written a patch for quotas which should fix various races and
also maybe your problem. I'd be delighted if you can try it and send me
results.

Thanks Honza.

PS: patch against 2.2.6 is attached (I haven't tried to compile it with 2.2.6
yet but I already have one content user of this patch with this kernel ;-)).


--- linux/include/linux/fs.h Tue Apr 20 22:34:09 1999
+++ linux/include/linux/fs.h Tue Apr 20 23:10:14 1999
@@ -649,7 +649,7 @@
int (*alloc_inode) (const struct inode *, unsigned long, uid_t);
void (*free_block) (const struct inode *, unsigned long);
void (*free_inode) (const struct inode *, unsigned long);
- int (*transfer) (struct inode *, struct iattr *, char, uid_t);
+ int (*transfer) (struct inode *, struct iattr *, uid_t);
};

struct file_system_type {
--- linux/include/linux/quotaops.h Tue Apr 20 22:28:17 1999
+++ linux/include/linux/quotaops.h Tue Apr 20 23:08:22 1999
@@ -31,8 +31,8 @@
extern void dquot_free_block(const struct inode *inode, unsigned long number);
extern void dquot_free_inode(const struct inode *inode, unsigned long number);

-extern int dquot_transfer(struct inode *inode, struct iattr *iattr,
- char direction, uid_t initiator);
+extern int dquot_transfer(struct dentry *dentry, struct iattr *iattr,
+ uid_t initiator);

/*
* Operations supported for diskquotas.
@@ -101,11 +101,7 @@
if (dentry->d_inode->i_sb->dq_op) {
if (IS_QUOTAINIT(dentry->d_inode) == 0)
dentry->d_inode->i_sb->dq_op->initialize(dentry->d_inode, -1);
- if (dentry->d_inode->i_sb->dq_op->transfer(dentry->d_inode, iattr, 0, current->fsuid))
- goto out;
- error = notify_change(dentry, iattr);
- if (error)
- dentry->d_inode->i_sb->dq_op->transfer(dentry->d_inode, iattr, 1, current->fsuid);
+ error = dentry->d_inode->i_sb->dq_op->transfer(dentry, iattr, current->fsuid);
} else {
error = notify_change(dentry, iattr);
}
--- linux/fs/dquot.c Tue Apr 20 22:27:16 1999
+++ linux/fs/dquot.c Wed Apr 21 00:04:42 1999
@@ -21,6 +21,14 @@
* Revised list management to avoid races
* -- Bill Hawes, <whawes@star.net>, 9/98
*
+ * Fixed races in dquot_transfer(), dqget() and dquot_alloc_...().
+ * As the consequence the locking was moved from dquot_decr_...(),
+ * dquot_incr_...() to calling functions.
+ * invalidate_dquots() now writes modified dquots (otherwise we
+ * could discard some changes).
+ * Fixed a few bugs in grow_dquots. Also some other cosmetic changes.
+ * Jan Kara, <jack@atrey.karlin.mff.cuni.cz>, 4/99
+ *
* (C) Copyright 1994 - 1997 Marco van Wieringen
*/

@@ -166,7 +174,8 @@
{
/* sanity check */
if (list_empty(&dquot->dq_free)) {
- printk("remove_free_dquot: dquot not on free list??\n");
+ printk("remove_free_dquot: dquot not on the free list??\n");
+ return; /* J.K. Just don't do anything */
}
list_del(&dquot->dq_free);
INIT_LIST_HEAD(&dquot->dq_free);
@@ -306,10 +315,11 @@

void invalidate_dquots(kdev_t dev, short type)
{
- struct dquot *dquot, *next = inuse_list;
+ struct dquot *dquot, *next;
int need_restart;

restart:
+ next = inuse_list; /* Here it is better. Otherwise the restart doesn't have any sense ;-) */
need_restart = 0;
while ((dquot = next) != NULL) {
next = dquot->dq_next;
@@ -317,6 +327,8 @@
continue;
if (dquot->dq_type != type)
continue;
+ if (!dquot->dq_mnt) /* Already invalidated entry? */
+ continue;
if (dquot->dq_flags & DQ_LOCKED) {
__wait_on_dquot(dquot);

@@ -329,6 +341,18 @@
continue;
if (dquot->dq_type != type)
continue;
+ if (!dquot->dq_mnt)
+ continue;
+ }
+ /*
+ * Because inodes needn't to be the only holders of dquot
+ * the quota needn't to be written to disk. So we write it
+ * ourselves before discarding the data just for sure...
+ */
+ if (dquot->dq_flags & DQ_MOD && dquot->dq_mnt)
+ {
+ write_dquot(dquot);
+ need_restart = 1; /* We slept on IO */
}
clear_dquot(dquot);
}
@@ -342,10 +366,11 @@

int sync_dquots(kdev_t dev, short type)
{
- struct dquot *dquot, *next = inuse_list;
+ struct dquot *dquot, *next;
int need_restart;

restart:
+ next = inuse_list;
need_restart = 0;
while ((dquot = next) != NULL) {
next = dquot->dq_next;
@@ -353,6 +378,8 @@
continue;
if (type != -1 && dquot->dq_type != type)
continue;
+ if (!dquot->dq_mnt) /* Invalidated? */
+ continue;
if (!(dquot->dq_flags & (DQ_LOCKED | DQ_MOD)))
continue;

@@ -407,8 +434,16 @@
/* sanity check */
if (!list_empty(&dquot->dq_free)) {
printk("dqput: dquot already on free list??\n");
+ dquot->dq_count--; /* J.K. Just decrementing use count seems safer... */
+ return;
}
if (--dquot->dq_count == 0) {
+ /* Sanity check. Locked quota without owner isn't good idea... */
+ if (dquot->dq_flags & DQ_LOCKED) {
+ printk(KERN_ERR "VFS: Locked quota to be put on the free list.\n");
+ dquot->dq_flags &= ~DQ_LOCKED;
+ }
+ dquot->dq_flags &= ~DQ_MOD; /* Modified flag has no sense on free list */
/* Place at end of LRU free queue */
put_dquot_last(dquot);
wake_up(&dquot_wait);
@@ -417,23 +452,25 @@
return;
}

-static void grow_dquots(void)
+static int grow_dquots(void)
{
struct dquot *dquot;
- int cnt = 32;
+ int cnt = 0;

- while (cnt > 0) {
+ while (cnt < 32) {
dquot = kmem_cache_alloc(dquot_cachep, SLAB_KERNEL);
if(!dquot)
- return;
+ return cnt;

nr_dquots++;
memset((caddr_t)dquot, 0, sizeof(struct dquot));
+ init_waitqueue(&dquot->dq_wait);
/* all dquots go on the inuse_list */
put_inuse(dquot);
put_dquot_head(dquot);
- cnt--;
+ cnt++;
}
+ return cnt;
}

static struct dquot *find_best_candidate_weighted(void)
@@ -445,6 +482,7 @@

while ((tmp = tmp->next) != &free_dquots && --limit) {
dquot = list_entry(tmp, struct dquot, dq_free);
+ /* This should never happen... */
if (dquot->dq_flags & (DQ_LOCKED | DQ_MOD))
continue;
myscore = dquot->dq_referenced;
@@ -480,20 +518,9 @@
if (!dquot)
goto pressure;
got_it:
- if (dquot->dq_flags & (DQ_LOCKED | DQ_MOD)) {
- wait_on_dquot(dquot);
- if (dquot->dq_flags & DQ_MOD)
- {
- if(dquot->dq_mnt != (struct vfsmount *)NULL)
- write_dquot(dquot);
- }
- /*
- * The dquot may be back in use now, so we
- * must recheck the free list.
- */
- goto repeat;
- }
- /* sanity check ... */
+ /* Sanity checks */
+ if (dquot->dq_flags & DQ_LOCKED)
+ printk(KERN_ERR "VFS: Locked dquot on the free list\n");
if (dquot->dq_count != 0)
printk(KERN_ERR "VFS: free dquot count=%d\n", dquot->dq_count);

@@ -504,10 +531,9 @@
return dquot;

pressure:
- if (nr_dquots < max_dquots) {
- grow_dquots();
- goto repeat;
- }
+ if (nr_dquots < max_dquots)
+ if (grow_dquots())
+ goto repeat;

dquot = find_best_candidate_weighted();
if (dquot)
@@ -567,12 +593,32 @@
while (dquot_updating[hashent])
sleep_on(&update_wait);

+ if (!dquot->dq_mnt) { /* Has somebody invalidated entry under us? */
+ /*
+ * Do it as if the quota was invalidated before we started
+ */
+ dqput(dquot);
+ return NODQUOT;
+ }
dquot->dq_referenced++;
dqstats.lookups++;

return dquot;
}

+static struct dquot *dqduplicate(struct dquot *dquot)
+{
+ if (dquot == NODQUOT || !dquot->dq_mnt)
+ return NODQUOT;
+ dquot->dq_count++;
+ wait_on_dquot(dquot);
+ if (!dquot->dq_mnt) {
+ dquot->dq_count--;
+ return NODQUOT;
+ }
+ return dquot;
+}
+
static void add_dquot_ref(kdev_t dev, short type)
{
struct super_block *sb = get_super(dev);
@@ -646,23 +692,18 @@

static inline void dquot_incr_inodes(struct dquot *dquot, unsigned long number)
{
- lock_dquot(dquot);
dquot->dq_curinodes += number;
dquot->dq_flags |= DQ_MOD;
- unlock_dquot(dquot);
}

static inline void dquot_incr_blocks(struct dquot *dquot, unsigned long number)
{
- lock_dquot(dquot);
dquot->dq_curblocks += number;
dquot->dq_flags |= DQ_MOD;
- unlock_dquot(dquot);
}

static inline void dquot_decr_inodes(struct dquot *dquot, unsigned long number)
{
- lock_dquot(dquot);
if (dquot->dq_curinodes > number)
dquot->dq_curinodes -= number;
else
@@ -671,12 +712,10 @@
dquot->dq_itime = (time_t) 0;
dquot->dq_flags &= ~DQ_INODES;
dquot->dq_flags |= DQ_MOD;
- unlock_dquot(dquot);
}

static inline void dquot_decr_blocks(struct dquot *dquot, unsigned long number)
{
- lock_dquot(dquot);
if (dquot->dq_curblocks > number)
dquot->dq_curblocks -= number;
else
@@ -685,7 +724,6 @@
dquot->dq_btime = (time_t) 0;
dquot->dq_flags &= ~DQ_BLKS;
dquot->dq_flags |= DQ_MOD;
- unlock_dquot(dquot);
}

static inline char need_print_warning(short type, uid_t initiator, struct dquot *dquot)
@@ -869,9 +907,11 @@
if (dquot == NODQUOT)
goto out;

+ lock_dquot(dquot); /* We must protect against invalidating the quota */
error = -EFAULT;
if (dqblk && !copy_to_user(dqblk, &dquot->dq_dqb, sizeof(struct dqblk)))
error = 0;
+ unlock_dquot(dquot);
dqput(dquot);
out:
return error;
@@ -963,6 +1003,8 @@
break;
}
dquot = dqget(inode->i_dev, id, cnt);
+ if (dquot == NODQUOT)
+ continue;
if (inode->i_dquot[cnt] != NODQUOT) {
dqput(dquot);
continue;
@@ -1000,23 +1042,36 @@
int dquot_alloc_block(const struct inode *inode, unsigned long number, uid_t initiator,
char warn)
{
- unsigned short cnt;
+ int cnt;
struct tty_struct *tty = current->tty;
+ struct dquot *dquot[MAXQUOTAS];

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ dquot[cnt] = dqduplicate(inode->i_dquot[cnt]);
+ if (dquot[cnt] == NODQUOT)
continue;
- if (check_bdq(inode->i_dquot[cnt], cnt, number, initiator, tty, warn))
- return(NO_QUOTA);
+ lock_dquot(dquot[cnt]);
+ if (check_bdq(dquot[cnt], cnt, number, initiator, tty, warn))
+ goto put_all;
}

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ if (dquot[cnt] == NODQUOT)
continue;
- dquot_incr_blocks(inode->i_dquot[cnt], number);
+ dquot_incr_blocks(dquot[cnt], number);
+ unlock_dquot(dquot[cnt]);
+ dqput(dquot[cnt]);
}

- return(QUOTA_OK);
+ return QUOTA_OK;
+put_all:
+ for (; cnt >= 0; cnt--) {
+ if (dquot[cnt] == NODQUOT)
+ continue;
+ unlock_dquot(dquot[cnt]);
+ dqput(dquot[cnt]);
+ }
+ return NO_QUOTA;
}

/*
@@ -1024,23 +1079,36 @@
*/
int dquot_alloc_inode(const struct inode *inode, unsigned long number, uid_t initiator)
{
- unsigned short cnt;
+ int cnt;
struct tty_struct *tty = current->tty;
+ struct dquot *dquot[MAXQUOTAS];

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ dquot[cnt] = dqduplicate(inode -> i_dquot[cnt]);
+ if (dquot[cnt] == NODQUOT)
continue;
- if (check_idq(inode->i_dquot[cnt], cnt, number, initiator, tty))
- return(NO_QUOTA);
+ lock_dquot(dquot[cnt]);
+ if (check_idq(dquot[cnt], cnt, number, initiator, tty))
+ goto put_all;
}

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ if (dquot[cnt] == NODQUOT)
continue;
- dquot_incr_inodes(inode->i_dquot[cnt], number);
+ dquot_incr_inodes(dquot[cnt], number);
+ unlock_dquot(dquot[cnt]);
+ dqput(dquot[cnt]);
}

- return(QUOTA_OK);
+ return QUOTA_OK;
+put_all:
+ for (; cnt >= 0; cnt--) {
+ if (dquot[cnt] == NODQUOT)
+ continue;
+ unlock_dquot(dquot[cnt]);
+ dqput(dquot[cnt]);
+ }
+ return NO_QUOTA;
}

/*
@@ -1049,11 +1117,14 @@
void dquot_free_block(const struct inode *inode, unsigned long number)
{
unsigned short cnt;
+ struct dquot *dquot;

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ dquot = inode->i_dquot[cnt];
+ if (dquot == NODQUOT)
continue;
- dquot_decr_blocks(inode->i_dquot[cnt], number);
+ wait_on_dquot(dquot);
+ dquot_decr_blocks(dquot, number);
}
}

@@ -1063,11 +1134,14 @@
void dquot_free_inode(const struct inode *inode, unsigned long number)
{
unsigned short cnt;
+ struct dquot *dquot;

for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
- if (inode->i_dquot[cnt] == NODQUOT)
+ dquot = inode->i_dquot[cnt];
+ if (dquot == NODQUOT)
continue;
- dquot_decr_inodes(inode->i_dquot[cnt], number);
+ wait_on_dquot(dquot);
+ dquot_decr_inodes(dquot, number);
}
}

@@ -1076,14 +1150,18 @@
*
* Note: this is a blocking operation.
*/
-int dquot_transfer(struct inode *inode, struct iattr *iattr, char direction, uid_t initiator)
+int dquot_transfer(struct dentry *dentry, struct iattr *iattr, uid_t initiator)
{
+ struct inode *inode = dentry -> d_inode;
unsigned long blocks;
struct dquot *transfer_from[MAXQUOTAS];
struct dquot *transfer_to[MAXQUOTAS];
struct tty_struct *tty = current->tty;
short cnt, disc;
+ int error = -EDQUOT;

+ if (!inode)
+ return -ENOENT;
/*
* Find out if this filesystem uses i_blocks.
*/
@@ -1107,27 +1185,59 @@
case USRQUOTA:
if (inode->i_uid == iattr->ia_uid)
continue;
- transfer_from[cnt] = dqget(inode->i_dev, (direction) ? iattr->ia_uid : inode->i_uid, cnt);
- transfer_to[cnt] = dqget(inode->i_dev, (direction) ? inode->i_uid : iattr->ia_uid, cnt);
+ transfer_from[cnt] = dqget(inode->i_dev, inode->i_uid, cnt);
+ transfer_to[cnt] = dqget(inode->i_dev, iattr->ia_uid, cnt);
break;
case GRPQUOTA:
if (inode->i_gid == iattr->ia_gid)
continue;
- transfer_from[cnt] = dqget(inode->i_dev, (direction) ? iattr->ia_gid : inode->i_gid, cnt);
- transfer_to[cnt] = dqget(inode->i_dev, (direction) ? inode->i_gid : iattr->ia_gid, cnt);
+ transfer_from[cnt] = dqget(inode->i_dev, inode->i_gid, cnt);
+ transfer_to[cnt] = dqget(inode->i_dev, iattr->ia_gid, cnt);
break;
}

- if (check_idq(transfer_to[cnt], cnt, 1, initiator, tty) == NO_QUOTA ||
- check_bdq(transfer_to[cnt], cnt, blocks, initiator, tty, 0) == NO_QUOTA) {
- for (disc = 0; disc <= cnt; disc++) {
- dqput(transfer_from[disc]);
- dqput(transfer_to[disc]);
+ /* Something bad (eg. quotaoff) happened while we were sleeping? */
+ if (transfer_from[cnt] == NODQUOT || transfer_to[cnt] == NODQUOT)
+ {
+ if (transfer_from[cnt] != NODQUOT) {
+ dqput(transfer_from[cnt]);
+ transfer_from[cnt] = NODQUOT;
+ }
+ if (transfer_to[cnt] != NODQUOT) {
+ dqput(transfer_to[cnt]);
+ transfer_to[cnt] = NODQUOT;
}
- return(NO_QUOTA);
+ continue;
+ }
+ /*
+ * We have to lock the quotas to prevent races...
+ */
+ if (transfer_from[cnt] < transfer_to[cnt])
+ {
+ lock_dquot(transfer_from[cnt]);
+ lock_dquot(transfer_to[cnt]);
+ }
+ else
+ {
+ lock_dquot(transfer_to[cnt]);
+ lock_dquot(transfer_from[cnt]);
+ }
+
+ /*
+ * The entries might got invalidated while locking. The second
+ * dqget() could block and so the first structure might got
+ * invalidated or locked...
+ */
+ if (!transfer_to[cnt]->dq_mnt || !transfer_from[cnt]->dq_mnt ||
+ check_idq(transfer_to[cnt], cnt, 1, initiator, tty) == NO_QUOTA ||
+ check_bdq(transfer_to[cnt], cnt, blocks, initiator, tty, 0) == NO_QUOTA) {
+ cnt++;
+ goto put_all;
}
}

+ if ((error = notify_change(dentry, iattr)))
+ goto put_all;
/*
* Finally perform the needed transfer from transfer_from to transfer_to,
* and release any pointers to dquots not needed anymore.
@@ -1139,28 +1249,39 @@
if (transfer_from[cnt] == NODQUOT && transfer_to[cnt] == NODQUOT)
continue;

- if (transfer_from[cnt] != NODQUOT) {
- dquot_decr_inodes(transfer_from[cnt], 1);
- dquot_decr_blocks(transfer_from[cnt], blocks);
- }
+ dquot_decr_inodes(transfer_from[cnt], 1);
+ dquot_decr_blocks(transfer_from[cnt], blocks);

- if (transfer_to[cnt] != NODQUOT) {
- dquot_incr_inodes(transfer_to[cnt], 1);
- dquot_incr_blocks(transfer_to[cnt], blocks);
- }
+ dquot_incr_inodes(transfer_to[cnt], 1);
+ dquot_incr_blocks(transfer_to[cnt], blocks);

+ unlock_dquot(transfer_from[cnt]);
+ dqput(transfer_from[cnt]);
if (inode->i_dquot[cnt] != NODQUOT) {
struct dquot *temp = inode->i_dquot[cnt];
inode->i_dquot[cnt] = transfer_to[cnt];
+ unlock_dquot(transfer_to[cnt]);
dqput(temp);
- dqput(transfer_from[cnt]);
} else {
- dqput(transfer_from[cnt]);
+ unlock_dquot(transfer_to[cnt]);
dqput(transfer_to[cnt]);
}
}

- return(QUOTA_OK);
+ return 0;
+put_all:
+ for (disc = 0; disc < cnt; disc++) {
+ /* There should be none or both pointers set but... */
+ if (transfer_to[disc] != NODQUOT) {
+ unlock_dquot(transfer_to[disc]);
+ dqput(transfer_to[disc]);
+ }
+ if (transfer_from[disc] != NODQUOT) {
+ unlock_dquot(transfer_from[disc]);
+ dqput(transfer_from[disc]);
+ }
+ }
+ return error;
}


@@ -1324,8 +1445,8 @@
vfsmnt->mnt_dquot.files[type] = filp;

dquot = dqget(dev, 0, type);
- vfsmnt->mnt_dquot.inode_expire[type] = (dquot) ? dquot->dq_itime : MAX_IQ_TIME;
- vfsmnt->mnt_dquot.block_expire[type] = (dquot) ? dquot->dq_btime : MAX_DQ_TIME;
+ vfsmnt->mnt_dquot.inode_expire[type] = (dquot != NODQUOT) ? dquot->dq_itime : MAX_IQ_TIME;
+ vfsmnt->mnt_dquot.block_expire[type] = (dquot != NODQUOT) ? dquot->dq_btime : MAX_DQ_TIME;
dqput(dquot);

vfsmnt->mnt_sb->dq_op = &dquot_operations;
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