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In our d_revalidate callback (afs_linux_dentry_revalidate), we currently 'goto bad_dentry' when we encounter any error. This can happen if we can't allocate memory or some other internal errors, or if the relevant afs_lookup call fails just due to plain network errors. For any of these cases, we'll treat the dentry as if it's no longer valid, so we'll return '0' and call d_invalidate() on the dentry. However, the behavior of d_invalidate changed, as mentioned in commit afbc199f1 (LINUX: Avoid d_invalidate() during afs_ShakeLooseVCaches()). After a certain point in the Linux kernel, d_invalidate() will also effectively d_drop() the given dentry, unhashing it. This can cause getcwd() calls to fail with ENOENT for those directories (as mentioned in afbc199f1), and can cause bind-mount calls to fail similarly during a small window. To avoid all of this, when we encounter an error that prevents us from checking if the dentry is valid or not, we need to return an error, instead of saying 'yes' or 'no'. So, change afs_linux_dentry_revalidate to jump to the 'done' label when we encounter such errors, and avoid calling d_drop/d_invalidate in such cases. This also lets us remove the 'lookup_good' variable and consolidate some of the related logic. Important note: in older Linux kernels, d_revalidate cannot return errors; callers just interpreted its return value as either 'valid' (non-zero) or 'not valid' (zero). The treatment of negative values as errors was introduced in Linux commit bcdc5e019d9f525a9f181a7de642d3a9c27c7610, which was included in 2.6.19. This is very old, but technically still above our stated requirements for the Linux kernel, so try to handle this case, by jumping to 'bad_dentry' still for those old kernels. Just do this with a version check, since no configure check can detect this (no function signatures changed), and the only Linux versions that are a concern are quite old. Change-Id: Ie530ce08463cf6b6899f056cb76ae4047c989ef2 Reviewed-on: https://gerrit.openafs.org/14417 Reviewed-by: Mark Vitale <mvitale@sinenomine.net> Reviewed-by: Cheyenne Wills <cwills@sinenomine.net> Tested-by: BuildBot <buildbot@rampaginggeek.com> Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
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.