From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 11 Apr 2019 03:25:15 +0100 From: Al Viro Subject: Re: [PATCH v2 1/2] vfs: use READ_ONCE() to access ->i_link Message-ID: <20190411022514.GC2217@ZenIV.linux.org.uk> References: <20190410202115.64501-1-ebiggers@kernel.org> <20190410202115.64501-2-ebiggers@kernel.org> <20190410210657.GA2217@ZenIV.linux.org.uk> <20190410231547.GC120258@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190410231547.GC120258@gmail.com> Sender: Al Viro To: Eric Biggers Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org List-ID: On Wed, Apr 10, 2019 at 04:15:48PM -0700, Eric Biggers wrote: > 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 > > > > > > 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(). Huh? Right you are - fsck knows how have I managed to misread that... Anyway, I can pick that READ_ONCE() patch through vfs.git if you wish, or it can go through your tree with my Acked-by - up to you...