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Background: By increasing the recordsize property above the default of 128KB, a filesystem may have "large" blocks. By default, a send stream of such a filesystem does not contain large WRITE records, instead it decreases objects' block sizes to 128KB and splits the large blocks into 128KB blocks, allowing the large-block filesystem to be received by a system that does not support the `large_blocks` feature. A send stream generated by `zfs send -L` (or `--large-block`) preserves the large block size on the receiving system, by using large WRITE records. When receiving an incremental send stream for a filesystem with large blocks, if the send stream's -L flag was toggled, a bug is encountered in which the file's contents are incorrectly zeroed out. The contents of any blocks that were not modified by this send stream will be lost. "Toggled" means that the previous send used `-L`, but this incremental does not use `-L` (-L to no-L); or that the previous send did not use `-L`, but this incremental does use `-L` (no-L to -L). Changes: This commit addresses the problem with several changes to the semantics of zfs send/receive: 1. "-L to no-L" incrementals are rejected. If the previous send used `-L`, but this incremental does not use `-L`, the `zfs receive` will fail with this error message: incremental send stream requires -L (--large-block), to match previous receive. 2. "no-L to -L" incrementals are handled correctly, preserving the smaller (128KB) block size of any already-received files that used large blocks on the sending system but were split by `zfs send` without the `-L` flag. 3. A new send stream format flag is added, `SWITCH_TO_LARGE_BLOCKS`. This feature indicates that we can correctly handle "no-L to -L" incrementals. This flag is currently not set on any send streams. In the future, we intend for incremental send streams of snapshots that have large blocks to use `-L` by default, and these streams will also have the `SWITCH_TO_LARGE_BLOCKS` feature set. This ensures that streams from the default use of `zfs send` won't encounter the bug mentioned above, because they can't be received by software with the bug. Implementation notes: To facilitate accessing the ZPL's generation number, `zfs_space_delta_cb()` has been renamed to `zpl_get_file_info()` and restructured to fill in a struct with ZPL-specific info including owner and generation. In the "no-L to -L" case, if this is a compressed send stream (from `zfs send -cL`), large WRITE records that are being written to small (128KB) blocksize files need to be decompressed so that they can be written split up into multiple blocks. The zio pipeline will recompress each smaller block individually. A new test case, `send-L_toggle`, is added, which tests the "no-L to -L" case and verifies that we get an error for the "-L to no-L" case. Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #6224 Closes #10383 |
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zfs.release.in |
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
META
file contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are 12-STABLE and 13-CURRENT.