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author | Ayush Ranjan <ayushranjan@google.com> | 2020-10-12 16:27:33 -0700 |
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committer | gVisor bot <gvisor-bot@google.com> | 2020-10-12 16:29:33 -0700 |
commit | e7bbe70f79aa9308c2eb54b057ee5779b22f478e (patch) | |
tree | eaead5c4e56fd0440fb40b02d056b8022a53ace2 /website/_includes/header-links.html | |
parent | 93bc0777be45994c4fcd7611a743f99fe73b36fa (diff) |
[vfs] kernfs: Fix inode memory leak issue.
This change aims to fix the memory leak issue reported inĀ #3933.
Background:
VFS2 kernfs kept accumulating invalid dentries if those dentries were not
walked on. After substantial consideration of the problem by our team, we
decided to have an LRU cache solution. This change is the first part to that
solution, where we don't cache anything. The LRU cache can be added on top of
this.
What has changed:
- Introduced the concept of an inode tree in kernfs.OrderedChildren.
This is helpful is cases where the lifecycle of an inode is different from
that of a dentry.
- OrderedChildren now deals with initialized inodes instead of initialized
dentries. It now implements Lookup() where it constructs a new dentry
using the inode.
- OrderedChildren holds a ref on all its children inodes. With this change,
now an inode can "outlive" a dentry pointing to it. See comments in
kernfs.OrderedChildren.
- The kernfs dentry tree is solely maintained by kernfs only. Inode
implementations can not modify the dentry tree.
- Dentries that reach ref count 0 are removed from the dentry tree.
- revalidateChildLocked now defer-DecRefs the newly created dentry from
Inode.Lookup(), limiting its life to the current filesystem operation. If
refs are picked on the dentry during the FS op (via an FD or something),
then it will stick around and will be removed when the FD is closed. So there
is essentially _no caching_ for Look()ed up dentries.
- kernfs.DecRef does not have the precondition that fs.mu must be locked.
Fixes #3933
PiperOrigin-RevId: 336768576
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