diff options
Diffstat (limited to 'pkg/sentry/fsimpl/overlay/overlay.go')
| -rw-r--r-- | pkg/sentry/fsimpl/overlay/overlay.go | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/overlay/overlay.go b/pkg/sentry/fsimpl/overlay/overlay.go index 9a8f7010e..b2efe5f80 100644 --- a/pkg/sentry/fsimpl/overlay/overlay.go +++ b/pkg/sentry/fsimpl/overlay/overlay.go @@ -22,6 +22,10 @@ // filesystem.renameMu // dentry.dirMu // dentry.copyMu +// *** "memmap.Mappable locks" below this point +// dentry.mapsMu +// *** "memmap.Mappable locks taken by Translate" below this point +// dentry.dataMu // // Locking dentry.dirMu in multiple dentries requires that parent dentries are // locked before child dentries, and that filesystem.renameMu is locked to @@ -37,6 +41,7 @@ import ( "gvisor.dev/gvisor/pkg/fspath" fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" + "gvisor.dev/gvisor/pkg/sentry/memmap" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" @@ -419,6 +424,35 @@ type dentry struct { devMinor uint32 ino uint64 + // If this dentry represents a regular file, then: + // + // - mapsMu is used to synchronize between copy-up and memmap.Mappable + // methods on dentry preceding mm.MemoryManager.activeMu in the lock order. + // + // - dataMu is used to synchronize between copy-up and + // dentry.(memmap.Mappable).Translate. + // + // - lowerMappings tracks memory mappings of the file. lowerMappings is + // used to invalidate mappings of the lower layer when the file is copied + // up to ensure that they remain coherent with subsequent writes to the + // file. (Note that, as of this writing, Linux overlayfs does not do this; + // this feature is a gVisor extension.) lowerMappings is protected by + // mapsMu. + // + // - If this dentry is copied-up, then wrappedMappable is the Mappable + // obtained from a call to the current top layer's + // FileDescription.ConfigureMMap(). Once wrappedMappable becomes non-nil + // (from a call to nonDirectoryFD.ensureMappable()), it cannot become nil. + // wrappedMappable is protected by mapsMu and dataMu. + // + // - isMappable is non-zero iff wrappedMappable is non-nil. isMappable is + // accessed using atomic memory operations. + mapsMu sync.Mutex + lowerMappings memmap.MappingSet + dataMu sync.RWMutex + wrappedMappable memmap.Mappable + isMappable uint32 + locks vfs.FileLocks } |