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unionfs uses a per-directory hashtable to cache subdirectory nodes. Currently this hashtable is looked up using the directory name, but since unionfs nodes aren't removed from the cache until they're reclaimed, this poses some problems. For example, if a directory is created on a unionfs mount shortly after deleting a previous directory with the same path, the cache may end up reusing the node for the previous directory, including its upper/lower FS vnodes. Operations against those vnodes with then likely fail because the vnodes represent deleted files; for example UFS will reject VOP_MKDIR() against such a vnode because its effective link count is 0. This may then manifest as e.g. mkdir(2) or open(2) returning ENOENT for an attempt to create a file under the re-created directory. While it would be possible to fix this by explicitly managing the name-based cache during delete or rename operations, or by rejecting cache hits if the underlying FS vnodes don't match those passed to unionfs_nodeget(), it seems cleaner to instead hash the unionfs nodes based on their underlying FS vnodes. Since unionfs prefers to operate against the upper vnode if one is present, the lower vnode will only be used for hashing as long as the upper vnode is NULL. This should also make hashing faster by eliminating string traversal and using the already-computed hash index stored in each vnode. While here, fix a couple of other cache-related issues: --Remove 8 bytes of unnecessary baggage from each unionfs node by getting rid of the stored hash mask field. The mask is knowable at compile time. --When a matching node is found in the cache, reference its vnode using vrefl() while still holding the vnode interlock. Previously unionfs_nodeget() would vref() the vnode after the interlock was dropped, but the vnode may be reclaimed during that window. This caused intermittent panics from vn_lock(9) during unionfs stress testing. Reviewed by: kib, markj Tested by: pho Differential Revision: https://reviews.freebsd.org/D32533 |
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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.
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 | Various commands and libraries under the GNU Public License. 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. |
sys/arch/conf |
Kernel configuration files. GENERIC is the configuration used in release builds. NOTES contains documentation of all possible entries. |
| 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.