f734301d22
Implement semi-compatible functionality for mode=0 (preallocation) and mode=FALLOC_FL_KEEP_SIZE (preallocation beyond EOF) for ZPL. Since ZFS does COW and snapshots, preallocating blocks for a file cannot guarantee that writes to the file will not run out of space. Even if the first overwrite was guaranteed, it would not handle any later overwrite of blocks due to COW, so strict compliance is futile. Instead, make a best-effort check that at least enough free space is currently available in the pool (with a bit of margin), then create a sparse file of the requested size and continue on with life. This does not handle all cases (e.g. several fallocate() calls before writing into the files when the filesystem is nearly full), which would require a more complex mechanism to be implemented, probably based on a modified version of dmu_prealloc(), but is usable as-is. A new module option zfs_fallocate_reserve_percent is used to control the reserve margin for any single fallocate call. By default, this is 110% of the requested preallocation size, so an additional 10% of available space is reserved for overhead to allow the application a good chance of finishing the write when the fallocate() succeeds. If the heuristics of this basic fallocate implementation are not desirable, the old non-functional behavior of returning EOPNOTSUPP for calls can be restored by setting zfs_fallocate_reserve_percent=0. The parameter of zfs_statvfs() is changed to take an inode instead of a dentry, since no dentry is available in zfs_fallocate_common(). A few tests from @behlendorf cover basic fallocate functionality. Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Arshad Hussain <arshad.super@gmail.com> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Co-authored-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andreas Dilger <adilger@dilger.ca> Issue #326 Closes #10408
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL Site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite Linux distribution can be found at the ZoL Site.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are 12-STABLE and 13-CURRENT.