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With recent changes to d_invalidate's semantics (it returns void in Linux 3.11, and always returns success in RHEL 7.4), it has become increasingly clear that d_invalidate() is not the best function for use in our best-effort (nondisruptive) attempt to free up vcaches that is afs_ShakeLooseVCaches(). The new d_invalidate() semantics always force the invalidation of a directory dentry, which contradicts our desire to be nondisruptive, especially when that directory is being used as the current working directory for a process. Our call to d_invalidate(), intended to merely probe for whether a dentry can be discarded without affecting other consumers, instead would cause processes using that dentry as a CWD to receive ENOENT errors from getcwd(). A previous commit (c3bbf0b4444db88192eea4580ac9e9ca3de0d286) tried to address this issue by calling d_prune_aliases() instead of d_invalidate(), but d_prune_aliases() does not recursively descend into children of the given dentry while pruning, leaving it an incomplete solution for our use-case. To address these issues, modify the shakeloose routine TryEvictDentries() to call shrink_dcache_parent() and maybe __d_drop() for directories, and d_prune_aliases() for non-directories, instead of d_invalidate(). (Calls to d_prune_aliases() for directories have already been removed by reverting commit c3bbf0b4444db88192eea4580ac9e9ca3de0d286.) Just like d_invalidate(), shrink_dcache_parent() has been around "forever" (since pre-git v2.6.12). Also like d_invalidate(), it "walks" the parent dentry's subdirectories and "shrinks" (unhashes) unused dentries. But unlike d_invalidate(), shrink_dcache_parent() will not unhash an in-use dentry, and has never changed its signature or semantics. d_prune_aliases() has also been available "forever", and has also never changed its signature or semantics. The lack of recursive descent is not an issue for non-directories, which cannot have such children. [kaduk@mit.edu: apply review feedback to fix locking and avoid extraneous changes, and reword commit message] Change-Id: Icb6138ee5785e0ef82a9b85b1d2651dfd0830043 Reviewed-on: https://gerrit.openafs.org/12830 Reviewed-by: Benjamin Kaduk <kaduk@mit.edu> Tested-by: BuildBot <buildbot@rampaginggeek.com>
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.