fuse: return -ECONNABORTED on /dev/fuse read after abort

Currently the userspace has no way of knowing whether the fuse
connection ended because of umount or abort via sysfs. It makes it hard
for filesystems to free the mountpoint after abort without worrying
about removing some new mount.

The patch fixes it by returning different errors when userspace reads
from /dev/fuse (-ENODEV for umount and -ECONNABORTED for abort).

Add a new capability flag FUSE_ABORT_ERROR. If set and the connection is
gone because of sysfs abort, reading from the device will return
-ECONNABORTED.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index c4c093bbf456..7d2e7deea64b 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -515,6 +515,9 @@ struct fuse_conn {
 	    abort and device release */
 	unsigned connected;
 
+	/** Connection aborted via sysfs */
+	bool aborted;
+
 	/** Connection failed (version mismatch).  Cannot race with
 	    setting other bitfields since it is only set once in INIT
 	    reply, before any other request, and never cleared */
@@ -526,6 +529,9 @@ struct fuse_conn {
 	/** Do readpages asynchronously?  Only set in INIT */
 	unsigned async_read:1;
 
+	/** Return an unique read error after abort.  Only set in INIT */
+	unsigned abort_err:1;
+
 	/** Do not send separate SETATTR request before open(O_TRUNC)  */
 	unsigned atomic_o_trunc:1;
 
@@ -851,7 +857,7 @@ void fuse_request_send_background_locked(struct fuse_conn *fc,
 					 struct fuse_req *req);
 
 /* Abort all requests */
-void fuse_abort_conn(struct fuse_conn *fc);
+void fuse_abort_conn(struct fuse_conn *fc, bool is_abort);
 
 /**
  * Invalidate inode attributes