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Message-ID: <20200513214154.GB2140786@iweiny-DESK2.sc.intel.com> Date: Wed, 13 May 2020 14:41:55 -0700 From: Ira Weiny <ira.weiny@...el.com> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org, Andreas Dilger <adilger.kernel@...ger.ca>, "Theodore Y. Ts'o" <tytso@....edu>, Al Viro <viro@...iv.linux.org.uk>, Dan Williams <dan.j.williams@...el.com>, Dave Chinner <david@...morbit.com>, Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>, "Darrick J. Wong" <darrick.wong@...cle.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 8/9] fs/ext4: Introduce DAX inode flag On Wed, May 13, 2020 at 04:47:06PM +0200, Jan Kara wrote: > On Tue 12-05-20 22:43:23, ira.weiny@...el.com wrote: > > From: Ira Weiny <ira.weiny@...el.com> > > > > Add a flag to preserve FS_XFLAG_DAX in the ext4 inode. > > > > Set the flag to be user visible and changeable. Set the flag to be > > inherited. Allow applications to change the flag at any time. > > > > Finally, on regular files, flag the inode to not be cached to facilitate > > changing S_DAX on the next creation of the inode. > > > > Signed-off-by: Ira Weiny <ira.weiny@...el.com> > > > > --- > > Change from RFC: > > use new d_mark_dontcache() > > Allow caching if ALWAYS/NEVER is set > > Rebased to latest Linus master > > Change flag to unused 0x01000000 > > update ext4_should_enable_dax() > > --- > > fs/ext4/ext4.h | 13 +++++++++---- > > fs/ext4/inode.c | 4 +++- > > fs/ext4/ioctl.c | 25 ++++++++++++++++++++++++- > > 3 files changed, 36 insertions(+), 6 deletions(-) > > > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > > index 01d1de838896..715f8f2029b2 100644 > > --- a/fs/ext4/ext4.h > > +++ b/fs/ext4/ext4.h > > @@ -415,13 +415,16 @@ struct flex_groups { > > #define EXT4_VERITY_FL 0x00100000 /* Verity protected inode */ > > #define EXT4_EA_INODE_FL 0x00200000 /* Inode used for large EA */ > > /* 0x00400000 was formerly EXT4_EOFBLOCKS_FL */ > > + > > +#define EXT4_DAX_FL 0x01000000 /* Inode is DAX */ > > + > > #define EXT4_INLINE_DATA_FL 0x10000000 /* Inode has inline data. */ > > #define EXT4_PROJINHERIT_FL 0x20000000 /* Create with parents projid */ > > #define EXT4_CASEFOLD_FL 0x40000000 /* Casefolded file */ > > #define EXT4_RESERVED_FL 0x80000000 /* reserved for ext4 lib */ > > > > -#define EXT4_FL_USER_VISIBLE 0x705BDFFF /* User visible flags */ > > -#define EXT4_FL_USER_MODIFIABLE 0x604BC0FF /* User modifiable flags */ > > +#define EXT4_FL_USER_VISIBLE 0x715BDFFF /* User visible flags */ > > +#define EXT4_FL_USER_MODIFIABLE 0x614BC0FF /* User modifiable flags */ > > Hum, I think this was already mentioned but there are also definitions in > include/uapi/linux/fs.h which should be kept in sync... Also if DAX flag > gets modified through FS_IOC_SETFLAGS, we should call ext4_doncache() as > well, shouldn't we? Ah yea it was mentioned. Sorry. > > > @@ -802,6 +807,21 @@ static int ext4_ioctl_get_es_cache(struct file *filp, unsigned long arg) > > return error; > > } > > > > +static void ext4_dax_dontcache(struct inode *inode, unsigned int flags) > > +{ > > + struct ext4_inode_info *ei = EXT4_I(inode); > > + > > + if (S_ISDIR(inode->i_mode)) > > + return; > > + > > + if (test_opt2(inode->i_sb, DAX_NEVER) || > > + test_opt(inode->i_sb, DAX_ALWAYS)) > > + return; > > + > > + if (((ei->i_flags ^ flags) & EXT4_DAX_FL) == EXT4_DAX_FL) > > + d_mark_dontcache(inode); > > +} > > + > > long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > > { > > struct inode *inode = file_inode(filp); > > @@ -1267,6 +1287,9 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > > return err; > > > > inode_lock(inode); > > + > > + ext4_dax_dontcache(inode, flags); > > + > > I don't think we should set dontcache flag when setting of DAX flag fails - > it could event be a security issue). good point. > > So I think you'll have to check > whether DAX flag is being changed, ext4_dax_dontcache() does check if the flag is being changed. > call vfs_ioc_fssetxattr_check(), and > only if it succeeded and DAX flags was changing call ext4_dax_dontcache(). Yes I think it would be better to ensure all of the ioctl succeeds prior to setting the don't cache. The logic is easier to follow. Ira > > Honza > -- > Jan Kara <jack@...e.com> > SUSE Labs, CR
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