// A helper function for use after incrementing an inode's lookup count.
// Ensures that the lookup count is decremented again if the caller is going to
// return in error (in which case the kernel and gcsfuse would otherwise
// disagree about the lookup count for the inode's ID), so that the inode isn't
// leaked.
//
// Typical usage:
//
// func (fs *fileSystem) doFoo() (err error) {
// in, err := fs.lookUpOrCreateInodeIfNotStale(...)
// if err != nil {
// return
// }
//
// defer fs.unlockAndMaybeDisposeOfInode(in, &err)
//
// ...
// }
//
// LOCKS_EXCLUDED(fs.mu)
// UNLOCK_FUNCTION(in)
func (fs *fileSystem) unlockAndMaybeDisposeOfInode(
in inode.Inode,
err *error) {
// If there is no error, just unlock.
if *err == nil {
in.Unlock()
return
}
// Otherwise, go through the decrement helper, which requires the file system
// lock.
fs.mu.Lock()
fs.unlockAndDecrementLookupCount(in, 1)
}
// Decrement the supplied inode's lookup count, destroying it if the inode says
// that it has hit zero.
//
// We require the file system lock to exclude concurrent lookups, which might
// otherwise find an inode whose lookup count has gone to zero.
//
// UNLOCK_FUNCTION(fs.mu)
// UNLOCK_FUNCTION(in)
func (fs *fileSystem) unlockAndDecrementLookupCount(
in inode.Inode,
N uint64) {
name := in.Name()
// Decrement the lookup count.
shouldDestroy := in.DecrementLookupCount(N)
// Update file system state, orphaning the inode if we're going to destroy it
// below.
if shouldDestroy {
delete(fs.inodes, in.ID())
// Update indexes if necessary.
if fs.generationBackedInodes[name] == in {
delete(fs.generationBackedInodes, name)
}
if fs.implicitDirInodes[name] == in {
delete(fs.implicitDirInodes, name)
}
}
// We are done with the file system.
fs.mu.Unlock()
// Now we can destroy the inode if necessary.
if shouldDestroy {
destroyErr := in.Destroy()
if destroyErr != nil {
log.Printf("Error destroying inode %q: %v", name, destroyErr)
}
}
in.Unlock()
}