Re: [PATCH 2/7] mm: Protect operations adding pages to page cache with i_mapping_lock

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Apr 14, 2021 at 10:01:13AM +1000, Dave Chinner wrote:
> > +	if (iocb->ki_flags & IOCB_NOWAIT) {
> > +		if (!down_read_trylock(&mapping->host->i_mapping_sem))
> > +			return -EAGAIN;
> > +	} else {
> > +		down_read(&mapping->host->i_mapping_sem);
> > +	}
> 
> We really need a lock primitive for this. The number of times this
> exact lock pattern is being replicated all through the IO path is
> getting out of hand.
> 
> static inline bool
> down_read_try_or_lock(struct rwsem *sem, bool try)
> {
> 	if (try) {
> 		if (!down_read_trylock(sem))
> 			return false;
> 	} else {
> 		down_read(&mapping->host->i_mapping_sem);
> 	}
> 	return true;
> }
> 
> and the callers become:
> 
> 	if (!down_read_try_or_lock(sem, (iocb->ki_flags & IOCB_NOWAIT)))
> 		return -EAGAIN;

I think that should be written:

	if (!iocb_read_lock(iocb, &rwsem))
		return -EAGAIN;

and implemented as:

static inline int iocb_read_lock(struct kiocb *iocb, struct rwsem *sem)
{
	if (iocb->ki_flags & IOCB_NOWAIT)
		return down_read_trylock(sem) ? 0 : -EAGAIN;
	return down_read_killable(sem);
}




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux