From: "Kani, Toshi" Subject: Re: [PATCH 2/2] ext4, dax: set ext4_dax_aops for dax files Date: Wed, 12 Sep 2018 16:08:00 +0000 Message-ID: <1f1cf9db3981390d2ad5a08d5f1987d9c933e687.camel@hpe.com> References: <20180911154246.6844-1-toshi.kani@hpe.com> <20180911154246.6844-3-toshi.kani@hpe.com> <20180912093140.GB7782@quack2.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: "tytso-3s7WtUTddSA@public.gmane.org" , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" To: "dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "jack-AlSwsSmVLrQ@public.gmane.org" Return-path: In-Reply-To: <20180912093140.GB7782-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org> Content-Language: en-US Content-ID: <5406065F89EEF84085460FEB5A0ED63E-mmYPd6ayCNGroOM5E8FhRbjFIynDaujOfM0AETQt39g@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On Wed, 2018-09-12 at 11:31 +0200, Jan Kara wrote: > On Tue 11-09-18 11:15:18, Dan Williams wrote: > > On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani wrote: > > > Sync syscall to an existing DAX file needs to flush processor cache, > > > but it does not currently. This is because 'ext4_da_aops' is set to > > > address_space_operations of existing DAX files, instead of 'ext4_dax_aops', > > > since S_DAX flag is set after ext4_set_aops() in the open path. > > > > > > New file > > > -------- > > > lookup_open > > > ext4_create > > > __ext4_new_inode > > > ext4_set_inode_flags // Set S_DAX flag > > > ext4_set_aops // Set aops to ext4_dax_aops > > > > > > Existing file > > > ------------- > > > lookup_open > > > ext4_lookup > > > ext4_iget > > > ext4_set_aops // Set aops to ext4_da_aops > > > ext4_set_inode_flags // Set S_DAX flag > > > > > > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops(). > > > > > > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086 > > > > Same format nit: > > > > Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops") > > Cc: > > > > > > > Signed-off-by: Toshi Kani > > > Cc: Jan Kara > > > Cc: Dan Williams > > > Cc: "Theodore Ts'o" > > > Cc: Andreas Dilger > > > --- > > > fs/ext4/inode.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > > index 775cd9b4af55..93cbbb859c40 100644 > > > --- a/fs/ext4/inode.c > > > +++ b/fs/ext4/inode.c > > > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino) > > > if (ret) > > > goto bad_inode; > > > > > > + ext4_set_inode_flags(inode); > > > + > > > > Hmm, does this have unintended behavior changes? > > > > I notice that there are some checks for flags "IS_APPEND(inode) || > > IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I > > didn't look too much deeper at whether those checks are bogus, but it > > would seem safer to do something like this for a lower risk fix. > > > > Thoughts? > > Well, safer but it would leave the landmine around for others to hit. > Toshi, please move the ext4_set_inode_flags() call to be just after the > assignment: > > ei->i_flags = le32_to_cpu(raw_inode->i_flags); > > in ext4_iget(). That way people won't introduce checks for i_flags that can > never hit... And yes, it fixes also other bugs (mostly in sanity checks > AFAICS) than the DAX issue. Sure. Assuming you think the implicit change Dan pointed out is not a problem, yes, I will go with this cleaner approach. Thanks! -Toshi