From: Jan Kara Subject: Re: [PATCH 2/2] ext4, dax: set ext4_dax_aops for dax files Date: Wed, 12 Sep 2018 11:31:40 +0200 Message-ID: <20180912093140.GB7782@quack2.suse.cz> References: <20180911154246.6844-1-toshi.kani@hpe.com> <20180911154246.6844-3-toshi.kani@hpe.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , linux-nvdimm , Linux Kernel Mailing List , Andreas Dilger , Jan Kara , linux-ext4 To: Dan Williams Return-path: Content-Disposition: inline In-Reply-To: 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 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. Honza > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index d0dd585add6a..1e9ab445c777 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -4999,7 +4999,6 @@ struct inode *ext4_iget(struct super_block *sb, > unsigned long ino) > if (S_ISREG(inode->i_mode)) { > inode->i_op = &ext4_file_inode_operations; > inode->i_fop = &ext4_file_operations; > - ext4_set_aops(inode); > } else if (S_ISDIR(inode->i_mode)) { > inode->i_op = &ext4_dir_inode_operations; > inode->i_fop = &ext4_dir_operations; > @@ -5042,6 +5041,12 @@ struct inode *ext4_iget(struct super_block *sb, > unsigned long ino) > } > brelse(iloc.bh); > ext4_set_inode_flags(inode); > + /* > + * Now that we have determined whether DAX is enabled, set the > + * proper address spaces operations > + */ > + if (S_ISREG(inode->i_mode)) > + ext4_set_aops(inode); > > unlock_new_inode(inode); > return inode; -- Jan Kara SUSE Labs, CR