Re: [PATCH v2 1/2] vfs: use READ_ONCE() to access ->i_link

[Eric Biggers <ebiggers@xxxxxxxxxx>]

On Wed, Apr 10, 2019 at 10:06:57PM +0100, Al Viro wrote:
> On Wed, Apr 10, 2019 at 01:21:14PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@xxxxxxxxxx>
> > 
> > Use 'READ_ONCE(inode->i_link)' to explicitly support filesystems caching
> > the symlink target in ->i_link later if it was unavailable at iget()
> > time, or wasn't easily available.  I'll be doing this in fscrypt, to
> > improve the performance of encrypted symlinks on ext4, f2fs, and ubifs.
> > 
> > ->i_link will start NULL and may later be set to a non-NULL value by a
> > smp_store_release() or cmpxchg_release().  READ_ONCE() is needed on the
> > read side.  smp_load_acquire() is unnecessary because only a data
> > dependency barrier is required.  (Thanks to Al for pointing this out.)
> 
> You've missed vfs_readlink()...

How so?  The patch already updates vfs_readlink().

- Eric

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