diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/fuse.txt | 48 |
1 files changed, 44 insertions, 4 deletions
diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt index 324df27704cc..a584f05403a4 100644 --- a/Documentation/filesystems/fuse.txt +++ b/Documentation/filesystems/fuse.txt @@ -124,6 +124,46 @@ For each connection the following files exist within this directory: Only the owner of the mount may read or write these files. +Interrupting filesystem operations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If a process issuing a FUSE filesystem request is interrupted, the +following will happen: + + 1) If the request is not yet sent to userspace AND the signal is + fatal (SIGKILL or unhandled fatal signal), then the request is + dequeued and returns immediately. + + 2) If the request is not yet sent to userspace AND the signal is not + fatal, then an 'interrupted' flag is set for the request. When + the request has been successfully transfered to userspace and + this flag is set, an INTERRUPT request is queued. + + 3) If the request is already sent to userspace, then an INTERRUPT + request is queued. + +INTERRUPT requests take precedence over other requests, so the +userspace filesystem will receive queued INTERRUPTs before any others. + +The userspace filesystem may ignore the INTERRUPT requests entirely, +or may honor them by sending a reply to the _original_ request, with +the error set to EINTR. + +It is also possible that there's a race between processing the +original request and it's INTERRUPT request. There are two possibilities: + + 1) The INTERRUPT request is processed before the original request is + processed + + 2) The INTERRUPT request is processed after the original request has + been answered + +If the filesystem cannot find the original request, it should wait for +some timeout and/or a number of new requests to arrive, after which it +should reply to the INTERRUPT request with an EAGAIN error. In case +1) the INTERRUPT request will be requeued. In case 2) the INTERRUPT +reply will be ignored. + Aborting a filesystem connection ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -351,10 +391,10 @@ but is caused by a pagefault. Solution is basically the same as above. -An additional problem is that while the write buffer is being -copied to the request, the request must not be interrupted. This -is because the destination address of the copy may not be valid -after the request is interrupted. +An additional problem is that while the write buffer is being copied +to the request, the request must not be interrupted/aborted. This is +because the destination address of the copy may not be valid after the +request has returned. This is solved with doing the copy atomically, and allowing abort while the page(s) belonging to the write buffer are faulted with |