Re: [PATCH V4 1/3] quota: Add reservation support for delayed block allocation

Mingming Cao
2009-01-06T04:32:28Z

在 2008-12-15一的 14:16 +0100，Jan Kara写道：
> Hi Minming,
>
> On Fri 12-12-08 12:47:36, Mingming Cao wrote:
> > Quota: Add quota reservation support
> >
> > Delayed allocation defers the block allocation at the dirty pages
> > flush-out time, doing quota charge/check at that time is too late.
> > But we can't charge the quota blocks until blocks are really allocated,
> > otherwise users could get overcharged after reboot from system crash.
> >
> > This patch adds quota reservation for delayed llocation. Quota blocks
> > are reserved in memory, inode and quota won't gets dirtied until later
> > block allocation time.
> >
> > Signed-off-by: Mingming Cao <cmm@us.ibm.com>
> >
> >
> > ---
> > fs/dquot.c | 109 +++++++++++++++++++++++++++++++++--------------
> > include/linux/quota.h | 2
> > include/linux/quotaops.h | 22 +++++++++
> > 3 files changed, 102 insertions(+), 31 deletions(-)
> >
> > Index: linux-2.6.28-rc2/fs/dquot.c
> > ===================================================================
> > --- linux-2.6.28-rc2.orig/fs/dquot.c 2008-11-06 13:36:21.000000000 -0800
> > +++ linux-2.6.28-rc2/fs/dquot.c 2008-12-12 12:20:45.000000000 -0800
> <snip>
> > @@ -1227,49 +1237,85 @@ void vfs_dq_drop(struct inode *inode)
> > /*
> > * This operation can block, but only after everything is updated
> > */
> > -int dquot_alloc_space(struct inode *inode, qsize_t number, int warn)
> > +int __dquot_alloc_space(struct inode *inode, qsize_t number,
> > + int warn, int reserve)
> > {
> > - int cnt, ret = NO_QUOTA;
> > + int cnt, ret = QUOTA_OK;
> > char warntype[MAXQUOTAS];
> >
> > - /* First test before acquiring mutex - solves deadlocks when we
> > - * re-enter the quota code and are already holding the mutex */
> > - if (IS_NOQUOTA(inode)) {
> > -out_add:
> > - inode_add_bytes(inode, number);
> > - return QUOTA_OK;
> > - }
> > for (cnt = 0; cnt < MAXQUOTAS; cnt++)
> > warntype[cnt] = QUOTA_NL_NOWARN;
> >
> > - down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > - if (IS_NOQUOTA(inode)) { /* Now we can do reliable test... */
> > - up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > - goto out_add;
> > - }
> > spin_lock(&dq_data_lock);
> > for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> > if (inode->i_dquot[cnt] == NODQUOT)
> > continue;
> > - if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt) == NO_QUOTA)
> > - goto warn_put_all;
> > + if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt)
> > + == NO_QUOTA) {
> > + ret = NO_QUOTA;
> > + goto out_unlock;
> > + }
> > }
> > for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> > if (inode->i_dquot[cnt] == NODQUOT)
> > continue;
> > - dquot_incr_space(inode->i_dquot[cnt], number);
> > + if (reserve)
> > + dquot_resv_space(inode->i_dquot[cnt], number);
> > + else{
> ^ here is missing space
>

Okay, will fix that.
> > + dquot_incr_space(inode->i_dquot[cnt], number);
> > + inode_add_bytes(inode, number);
> > + }
> > }
> > - inode_add_bytes(inode, number);
> > - ret = QUOTA_OK;
> > -warn_put_all:
> > - spin_unlock(&dq_data_lock);
> > - if (ret == QUOTA_OK)
> > - /* Dirtify all the dquots - this can block when journalling */
> > - for (cnt = 0; cnt < MAXQUOTAS; cnt++)
> > - if (inode->i_dquot[cnt])
> > - mark_dquot_dirty(inode->i_dquot[cnt]);
> > +out_unlock:
> > flush_warnings(inode->i_dquot, warntype);
> > + spin_unlock(&dq_data_lock);
> We can't do flush_warnings() inside the spinlock - that function can
> sleep. Please move the call outside the lock.
>

Ok, Will do.

Mingming

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