Message ID | 20200208193445.27421-5-ira.weiny@intel.com |
---|---|
State | Not Applicable |
Headers | show |
Series | Enable per-file/directory DAX operations V3 | expand |
On Sat, Feb 08, 2020 at 11:34:37AM -0800, ira.weiny@intel.com wrote: > From: Ira Weiny <ira.weiny@intel.com> > > Rather than open coding xfs_inode_supports_dax() in > xfs_ioctl_setattr_dax_invalidate() export xfs_inode_supports_dax() and > call it in preparation for swapping dax flags. > > This also means updating xfs_inode_supports_dax() to return true for a > directory. That's not correct. This now means S_DAX gets set on directory inodes because both xfs_inode_supports_dax() and the on-disk inode flag checks return true in xfs_diflags_to_iflags(). Hence when we instantiate a directory inode with a DAX inherit hint set on it we'll set S_DAX on the inode and so IS_DAX() will return true for directory inodes... Cheers, Dave.
On Tue, Feb 11, 2020 at 04:57:45PM +1100, Dave Chinner wrote: > On Sat, Feb 08, 2020 at 11:34:37AM -0800, ira.weiny@intel.com wrote: > > From: Ira Weiny <ira.weiny@intel.com> > > > > Rather than open coding xfs_inode_supports_dax() in > > xfs_ioctl_setattr_dax_invalidate() export xfs_inode_supports_dax() and > > call it in preparation for swapping dax flags. > > > > This also means updating xfs_inode_supports_dax() to return true for a > > directory. > > That's not correct. This now means S_DAX gets set on directory inodes > because both xfs_inode_supports_dax() and the on-disk inode flag > checks return true in xfs_diflags_to_iflags(). Hence when we > instantiate a directory inode with a DAX inherit hint set on it > we'll set S_DAX on the inode and so IS_DAX() will return true for > directory inodes... I'm not following. Don't we want S_DAX to get set on directory inodes? IIRC what we wanted was something like this where IS_DAX is the current state and "dax" is the inode flag: / <IS_DAX=0 dax=0> dir1 <IS_DAX=0 dax=0> f0 <IS_DAX=0 dax=0> f1 <IS_DAX=1 dax=1> dir2 <IS_DAX=1 dax=1> f2 <IS_DAX=1 dax=1> f3 <IS_DAX=0 dax=0> dir3 <IS_DAX=1 dax=1> f4 <IS_DAX=1 dax=1> dir4 <IS_DAX=0 dax=0> f5 <IS_DAX=0 dax=0> f6 <IS_DAX=1 dax=1> Where f1, dir2, f3, and dir4 required explicit state changes when they were created. Because they inherited their dax state from the parent. All the other creations happened based on the DAX state of the parent directory. So we need to store and know the state of the directories. What am I missing? Ira > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com
On Tue, Feb 11, 2020 at 08:28:30AM -0800, Ira Weiny wrote: > On Tue, Feb 11, 2020 at 04:57:45PM +1100, Dave Chinner wrote: > > On Sat, Feb 08, 2020 at 11:34:37AM -0800, ira.weiny@intel.com wrote: > > > From: Ira Weiny <ira.weiny@intel.com> > > > > > > Rather than open coding xfs_inode_supports_dax() in > > > xfs_ioctl_setattr_dax_invalidate() export xfs_inode_supports_dax() and > > > call it in preparation for swapping dax flags. > > > > > > This also means updating xfs_inode_supports_dax() to return true for a > > > directory. > > > > That's not correct. This now means S_DAX gets set on directory inodes > > because both xfs_inode_supports_dax() and the on-disk inode flag > > checks return true in xfs_diflags_to_iflags(). Hence when we > > instantiate a directory inode with a DAX inherit hint set on it > > we'll set S_DAX on the inode and so IS_DAX() will return true for > > directory inodes... > > I'm not following. Don't we want S_DAX to get set on directory inodes? No, because S_DAX is used for controlling direct user data access, and we *never* let users directly access directory data. Even the filesystems don't access directory data directly - the transactional change model of journaling filesystems requires metadata to be buffered in memory and never directly modified. Hence when filesystems like ext4 keep their directory data in the page cache, we do not want the kernel to think that this inode is accessed through the DAX subsystem - it is accessed via the buffered IO interfaces like page_cache_sync_readahead() and writeback is controlled by the journal. Hence setting S_DAX on these inodes is incorrect. Whilst XFS doesn't use the page cache for it's metadata buffering, the issue is the same as it's also a journalling filesystem. hence setting S_DAX on XFS directory inodes is also incorrect. > IIRC what we wanted was something like this where IS_DAX is the current state > and "dax" is the inode flag: > > / <IS_DAX=0 dax=0> > dir1 <IS_DAX=0 dax=0> > f0 <IS_DAX=0 dax=0> > f1 <IS_DAX=1 dax=1> > dir2 <IS_DAX=1 dax=1> > f2 <IS_DAX=1 dax=1> > f3 <IS_DAX=0 dax=0> > dir3 <IS_DAX=1 dax=1> > f4 <IS_DAX=1 dax=1> > dir4 <IS_DAX=0 dax=0> > f5 <IS_DAX=0 dax=0> > f6 <IS_DAX=1 dax=1> > > Where f1, dir2, f3, and dir4 required explicit state changes when they were > created. Because they inherited their dax state from the parent. All the > other creations happened based on the DAX state of the parent directory. So we > need to store and know the state of the directories. What am I missing? I think that you are conflating internal filesystem feature management details (the inheritance of the DAX flag feature of directories) with kernel IO path behaviour (the inode S_DAX flag). i.e. IS_DAX() indicates whether DAX is _actively being used_ to access the data of a regular file inode, not to indicate whether the on-disk flags used to manage default behaviour are set or not. Cheers, Dave.
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index 1a57be696810..da1eb2bdb386 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -1190,23 +1190,13 @@ xfs_ioctl_setattr_dax_invalidate( int *join_flags) { struct inode *inode = VFS_I(ip); - struct super_block *sb = inode->i_sb; int error; *join_flags = 0; - /* - * It is only valid to set the DAX flag on regular files and - * directories on filesystems where the block size is equal to the page - * size. On directories it serves as an inherited hint so we don't - * have to check the device for dax support or flush pagecache. - */ - if (fa->fsx_xflags & FS_XFLAG_DAX) { - struct xfs_buftarg *target = xfs_inode_buftarg(ip); - - if (!bdev_dax_supported(target->bt_bdev, sb->s_blocksize)) - return -EINVAL; - } + if ((fa->fsx_xflags & FS_XFLAG_DAX) == FS_XFLAG_DAX && + !xfs_inode_supports_dax(ip)) + return -EINVAL; /* If the DAX state is not changing, we have nothing to do here. */ if ((fa->fsx_xflags & FS_XFLAG_DAX) && diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c index a7db50d923d4..eebec159d873 100644 --- a/fs/xfs/xfs_iops.c +++ b/fs/xfs/xfs_iops.c @@ -1246,14 +1246,18 @@ xfs_inode_mount_is_dax( } /* Figure out if this file actually supports DAX. */ -static bool +bool xfs_inode_supports_dax( struct xfs_inode *ip) { struct xfs_mount *mp = ip->i_mount; /* Only supported on non-reflinked files. */ - if (!S_ISREG(VFS_I(ip)->i_mode) || xfs_is_reflink_inode(ip)) + if (xfs_is_reflink_inode(ip)) + return false; + + /* Only supported on regular files and directories. */ + if (!(S_ISREG(VFS_I(ip)->i_mode) || S_ISDIR(VFS_I(ip)->i_mode))) return false; /* Block size must match page size */ diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h index 4d24ff309f59..f24fec8de1d6 100644 --- a/fs/xfs/xfs_iops.h +++ b/fs/xfs/xfs_iops.h @@ -24,4 +24,6 @@ extern int xfs_setattr_nonsize(struct xfs_inode *ip, struct iattr *vap, extern int xfs_vn_setattr_nonsize(struct dentry *dentry, struct iattr *vap); extern int xfs_vn_setattr_size(struct dentry *dentry, struct iattr *vap); +extern bool xfs_inode_supports_dax(struct xfs_inode *ip); + #endif /* __XFS_IOPS_H__ */