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authorDean Deng <deandeng@google.com>2020-08-24 11:28:28 -0700
committergVisor bot <gvisor-bot@google.com>2020-08-24 11:30:44 -0700
commitbae25d2a087d4c493b3335803dbfe53ab5505267 (patch)
tree2f76a6540b90710b84c6275c06fbb85b21ad79a3 /pkg/sentry/vfs/g3doc
parent89791a79bf8365486d726133e50176bcee9d76e4 (diff)
Update inotify documentation for gofer filesystem.
We now allow hard links to be created within gofer fs (see github.com/google/gvisor/commit/f20e63e31b56784c596897e86f03441f9d05f567). Update the inotify documentation accordingly. PiperOrigin-RevId: 328177485
Diffstat (limited to 'pkg/sentry/vfs/g3doc')
-rw-r--r--pkg/sentry/vfs/g3doc/inotify.md18
1 files changed, 9 insertions, 9 deletions
diff --git a/pkg/sentry/vfs/g3doc/inotify.md b/pkg/sentry/vfs/g3doc/inotify.md
index e7da49faa..833db213f 100644
--- a/pkg/sentry/vfs/g3doc/inotify.md
+++ b/pkg/sentry/vfs/g3doc/inotify.md
@@ -28,9 +28,9 @@ The set of all watches held on a single file (i.e., the watch target) is stored
in vfs.Watches. Each watch will belong to a different inotify instance (an
instance can only have one watch on any watch target). The watches are stored in
a map indexed by their vfs.Inotify owner’s id. Hard links and file descriptions
-to a single file will all share the same vfs.Watches. Activity on the target
-causes its vfs.Watches to generate notifications on its watches’ inotify
-instances.
+to a single file will all share the same vfs.Watches (with the exception of the
+gofer filesystem, described in a later section). Activity on the target causes
+its vfs.Watches to generate notifications on its watches’ inotify instances.
### vfs.Watch
@@ -103,12 +103,12 @@ inotify:
unopened p9 file (and possibly an open FID), through which the Sentry
interacts with the gofer.
* *Solution:* Because there is no inode structure stored in the sandbox,
- inotify watches must be held on the dentry. This would be an issue in
- the presence of hard links, where multiple dentries would need to share
- the same set of watches, but in VFS2, we do not support the internal
- creation of hard links on gofer fs. As a result, we make the assumption
- that every dentry corresponds to a unique inode. However, the next point
- raises an issue with this assumption:
+ inotify watches must be held on the dentry. For the purposes of inotify,
+ we assume that every dentry corresponds to a unique inode, which may
+ cause unexpected behavior in the presence of hard links, where multiple
+ dentries should share the same set of watches. Indeed, it is impossible
+ for us to be absolutely sure whether dentries correspond to the same
+ file or not, due to the following point:
* **The Sentry cannot always be aware of hard links on the remote
filesystem.** There is no way for us to confirm whether two files on the
remote filesystem are actually links to the same inode. QIDs and inodes are