460ed6106c
The kernel handles the managment of UFS/FFS snapshots. Since UFS/FFS updates filesystem data (rather than always writing changes to new locations like ZFS), the kernel must check every filesystem write to see if the block being written is part of a snapshot. If it is part of a snapshot, then the kernel must make a copy of the old block value into a newly allocated block for the snapshot before allowing the write to be done. Similarly, if a block is being freed, the kernel must check to see if it is part of a snapshot and let the snapshot claim the block rather than freeing it for future use. When a snapshot is freed, its blocks need to be offered to older snapshots and freed only if no older snapshots wish to claim them. When snapshots were added to UFS/FFS they were integrated into soft updates and just a small part of the management of snapshots needed to be added to fsck_ffs(8) as soft updates minimized the set of snapshot changes that might need correction. When journaling was added to soft updates a much more complete knowledge of snapshots needed to be added to fsck_ffs(8) for it to be able to properly handle the filesystem changes that a journal rollback needs to do (specifically the freeing and allocation of blocks). Since this functionality was unavailable, the use of snapshots was disabled when running with journaled soft updates. This set of changes imports the kernel code for the management of snapshots to fsck_ffs(8). With this code in place it will become possible to enable snapshots when running with journalled soft updates. The most immediate benefit will be the ability to use snapshots to take consistent filesystem dumps on live filesystems. Future work will be done to update fsck_ffs(8) to be able to use snapshots to run in background on live filesystems running with journaled soft updates. Reviewed by: kib Tested by: Peter Holm Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D36491 |
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|---|---|---|
| .cirrus-ci | ||
| .github | ||
| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| stand | ||
| sys | ||
| targets | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| .cirrus.yml | ||
| .clang-format | ||
| .gitattributes | ||
| .gitignore | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| Makefile.sys.inc | ||
| ObsoleteFiles.inc | ||
| README.md | ||
| RELNOTES | ||
| UPDATING | ||
FreeBSD Source:
This is the top level of the FreeBSD source directory.
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory. Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7), config(8), FreeBSD handbook on building userland, and Handbook for kernels for more information, including setting make(1) variables.
For information on the CPU architectures and platforms supported by FreeBSD, see the FreeBSD website's Platforms page.
Source Roadmap:
| Directory | Description |
|---|---|
| bin | System/user commands. |
| cddl | Various commands and libraries under the Common Development and Distribution License. |
| contrib | Packages contributed by 3rd parties. |
| crypto | Cryptography stuff (see crypto/README). |
| etc | Template files for /etc. |
| gnu | Commands and libraries under the GNU General Public License (GPL) or Lesser General Public License (LGPL). Please see gnu/COPYING and gnu/COPYING.LIB for more information. |
| include | System include files. |
| kerberos5 | Kerberos5 (Heimdal) package. |
| lib | System libraries. |
| libexec | System daemons. |
| release | Release building Makefile & associated tools. |
| rescue | Build system for statically linked /rescue utilities. |
| sbin | System commands. |
| secure | Cryptographic libraries and commands. |
| share | Shared resources. |
| stand | Boot loader sources. |
| sys | Kernel sources (see sys/README.md). |
| targets | Support for experimental DIRDEPS_BUILD |
| tests | Regression tests which can be run by Kyua. See tests/README for additional information. |
| tools | Utilities for regression testing and miscellaneous tasks. |
| usr.bin | User commands. |
| usr.sbin | System administration commands. |
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see FreeBSD Handbook.