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Before Linux kernel commit 4919c5e45a91b5db5a41695fe0357fbdff0d5767, d_splice_alias in some cases can d_rehash the given dentry without attaching it to the given inode, right before the dentry is unhashed again. This means that for a few moments, that negative dentry is visible to __d_lookup, and thus is visible to path lookup and can be given to afs_linux_dentry_revalidate. Currently, afs_linux_dentry_revalidate will say that the dentry is valid, because d_time and other fields are set; it's just not attached to an inode. This causes an ENOENT error on lookup, even though the file is there (and no OpenAFS code said otherwise). Normally this race is rare, but it can be frequently exercised if we access the same directory via different names at the same time. This can happen with multiple mountpoints to the same volume, or by accessing an @sys directory via its abbreviated and expanded forms. To get around this, make afs_linux_dentry_revalidate check negative 'dentry's to see if they are unhashed. We also lock the parent inode, in order to guarantee that a problematic d_splice_alias call isn't running at the same time (and thus, we know the dentry will not be unhashed immediately afterwards). This slows down afs_linux_dentry_revalidate for valid negative 'dentry's a little, but it allows us to use negative dentry's at all. Linux kernel commit 4919c5e45a91b5db5a41695fe0357fbdff0d5767 fixes this issue, which was included in 2.6.34, so don't do this workaround for 2.6.34 and on. Change-Id: I8e58ebed4441151832054b1ef3f1aa5af1c4a9b5 Reviewed-on: https://gerrit.openafs.org/12638 Tested-by: BuildBot <buildbot@rampaginggeek.com> Reviewed-by: Benjamin Kaduk <kaduk@mit.edu> |
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| build-tools | ||
| doc | ||
| src | ||
| tests | ||
| .gitignore | ||
| .mailmap | ||
| .splintrc | ||
| acinclude.m4 | ||
| CODING | ||
| configure-libafs.ac | ||
| configure.ac | ||
| CONTRIBUTING | ||
| INSTALL | ||
| libafsdep | ||
| LICENSE | ||
| Makefile-libafs.in | ||
| Makefile.in | ||
| NEWS | ||
| NTMakefile | ||
| README | ||
| README-WINDOWS | ||
| regen.sh | ||
AFS is a distributed file system that enables users to share and access all of the files stored in a network of computers as easily as they access the files stored on their local machines. The file system is called distributed for this exact reason: files can reside on many different machines, but are available to users on every machine. OpenAFS 1.0 was originally released by IBM under the terms of the IBM Public License 1.0 (IPL10). For details on IPL10 see the LICENSE file in this directory. The current OpenAFS distribution is licensed under a combination of the IPL10 and many other licenses as granted by the relevant copyright holders. The LICENSE file in this directory contains more details, thought it is not a comprehensive statement. See INSTALL for information about building and installing OpenAFS on various platforms. See CODING for developer information and guidelines. See NEWS for recent changes to OpenAFS.