Messages in this thread | | | From | ira.weiny@intel ... | Subject | [PATCH 0/5] Enable per-file/directory DAX operations | Date | Sun, 20 Oct 2019 08:59:30 -0700 |
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From: Ira Weiny <ira.weiny@intel.com>
At LSF/MM'19 [1] [2] we discussed applications that overestimate memory consumption due to their inability to detect whether the kernel will instantiate page cache for a file, and cases where a global dax enable via a mount option is too coarse.
The following patch series enables selecting the use of DAX on individual files and/or directories on xfs, and lays some groundwork to do so in ext4. In this scheme the dax mount option can be omitted to allow the per-file property to take effect.
The insight at LSF/MM was to separate the per-mount or per-file "physical" capability switch from an "effective" attribute for the file.
At LSF/MM we discussed the difficulties of switching the mode of a file with active mappings / page cache. Rather than solve those races the decision was to just limit mode flips to 0-length files.
Finally, the physical DAX flag inheritance is maintained from previous work on XFS but should be added for other file systems for consistence.
[1] https://lwn.net/Articles/787973/ [2] https://lwn.net/Articles/787233/
To: linux-kernel@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Hellwig <hch@lst.de> Cc: "Theodore Y. Ts'o" <tytso@mit.edu> Cc: Jan Kara <jack@suse.cz> Cc: linux-ext4@vger.kernel.org Cc: linux-xfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org
Ira Weiny (5): fs/stat: Define DAX statx attribute fs/xfs: Isolate the physical DAX flag from effective fs/xfs: Separate functionality of xfs_inode_supports_dax() fs/xfs: Clean up DAX support check fs/xfs: Allow toggle of physical DAX flag
fs/stat.c | 3 +++ fs/xfs/xfs_ioctl.c | 32 ++++++++++++++------------------ fs/xfs/xfs_iops.c | 36 ++++++++++++++++++++++++++++++------ fs/xfs/xfs_iops.h | 2 ++ include/uapi/linux/stat.h | 1 + 5 files changed, 50 insertions(+), 24 deletions(-)
-- 2.20.1
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