[PATCH v4] fuse: return -ECONNABORTED on /dev/fuse read after abort

[Szymon Lukasz <noh4hss@gmail.com>]

Adds 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>
---
 fs/fuse/control.c         |  2 +-
 fs/fuse/cuse.c            |  4 ++--
 fs/fuse/dev.c             | 12 +++++++-----
 fs/fuse/fuse_i.h          |  8 +++++++-
 fs/fuse/inode.c           |  9 ++++++---
 include/uapi/linux/fuse.h |  7 ++++++-
 6 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index b9ea99c5b5b3..78fb7a07c5ca 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -35,7 +35,7 @@ static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
 {
 	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 	if (fc) {
-		fuse_abort_conn(fc);
+		fuse_abort_conn(fc, true);
 		fuse_conn_put(fc);
 	}
 	return count;
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index e9e97803442a..31d33b69957f 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -406,7 +406,7 @@ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 err_region:
 	unregister_chrdev_region(devt, 1);
 err:
-	fuse_abort_conn(fc);
+	fuse_abort_conn(fc, false);
 	goto out;
 }
 
@@ -581,7 +581,7 @@ static ssize_t cuse_class_abort_store(struct device *dev,
 {
 	struct cuse_conn *cc = dev_get_drvdata(dev);
 
-	fuse_abort_conn(&cc->fc);
+	fuse_abort_conn(&cc->fc, false);
 	return count;
 }
 static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 13c65dd2d37d..2e1beda0b82b 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1234,9 +1234,10 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
 	if (err)
 		goto err_unlock;
 
-	err = -ENODEV;
-	if (!fiq->connected)
+	if (!fiq->connected) {
+		err = (fc->aborted && fc->abort_err) ? -ECONNABORTED : -ENODEV;
 		goto err_unlock;
+	}
 
 	if (!list_empty(&fiq->interrupts)) {
 		req = list_entry(fiq->interrupts.next, struct fuse_req,
@@ -1287,7 +1288,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
 	spin_lock(&fpq->lock);
 	clear_bit(FR_LOCKED, &req->flags);
 	if (!fpq->connected) {
-		err = -ENODEV;
+		err = (fc->aborted && fc->abort_err) ? -ECONNABORTED : -ENODEV;
 		goto out_end;
 	}
 	if (err) {
@@ -2076,7 +2077,7 @@ static void end_polls(struct fuse_conn *fc)
  * is OK, the request will in that case be removed from the list before we touch
  * it.
  */
-void fuse_abort_conn(struct fuse_conn *fc)
+void fuse_abort_conn(struct fuse_conn *fc, bool is_abort)
 {
 	struct fuse_iqueue *fiq = &fc->iq;
 
@@ -2089,6 +2090,7 @@ void fuse_abort_conn(struct fuse_conn *fc)
 
 		fc->connected = 0;
 		fc->blocked = 0;
+		fc->aborted = is_abort;
 		fuse_set_initialized(fc);
 		list_for_each_entry(fud, &fc->devices, entry) {
 			struct fuse_pqueue *fpq = &fud->pq;
@@ -2151,7 +2153,7 @@ int fuse_dev_release(struct inode *inode, struct file *file)
 		/* Are we the last open device? */
 		if (atomic_dec_and_test(&fc->dev_count)) {
 			WARN_ON(fc->iq.fasync != NULL);
-			fuse_abort_conn(fc);
+			fuse_abort_conn(fc, false);
 		}
 		fuse_dev_free(fud);
 	}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index d5773ca67ad2..2f8a261d8669 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
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 94a745acaef8..46a17de24e14 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -371,7 +371,7 @@ void fuse_unlock_inode(struct inode *inode)
 
 static void fuse_umount_begin(struct super_block *sb)
 {
-	fuse_abort_conn(get_fuse_conn_super(sb));
+	fuse_abort_conn(get_fuse_conn_super(sb), false);
 }
 
 static void fuse_send_destroy(struct fuse_conn *fc)
@@ -393,7 +393,7 @@ static void fuse_put_super(struct super_block *sb)
 
 	fuse_send_destroy(fc);
 
-	fuse_abort_conn(fc);
+	fuse_abort_conn(fc, false);
 	mutex_lock(&fuse_mutex);
 	list_del(&fc->entry);
 	fuse_ctl_remove_conn(fc);
@@ -918,6 +918,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 				fc->posix_acl = 1;
 				fc->sb->s_xattr = fuse_acl_xattr_handlers;
 			}
+			if (arg->flags & FUSE_ABORT_ERROR)
+				fc->abort_err = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;
@@ -948,7 +950,8 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 		FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |
 		FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |
 		FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
-		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL;
+		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
+		FUSE_ABORT_ERROR;
 	req->in.h.opcode = FUSE_INIT;
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(*arg);
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 42fa977e3b14..f9b11c43c8f6 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -112,6 +112,9 @@
  *  7.26
  *  - add FUSE_HANDLE_KILLPRIV
  *  - add FUSE_POSIX_ACL
+ *
+ *  7.27
+ *  - add FUSE_ABORT_ERROR
  */
 
 #ifndef _LINUX_FUSE_H
@@ -147,7 +150,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 26
+#define FUSE_KERNEL_MINOR_VERSION 27
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -244,6 +247,7 @@ struct fuse_file_lock {
  * FUSE_PARALLEL_DIROPS: allow parallel lookups and readdir
  * FUSE_HANDLE_KILLPRIV: fs handles killing suid/sgid/cap on write/chown/trunc
  * FUSE_POSIX_ACL: filesystem supports posix acls
+ * FUSE_ABORT_ERROR: reading the device after abort returns ECONNABORTED
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -266,6 +270,7 @@ struct fuse_file_lock {
 #define FUSE_PARALLEL_DIROPS    (1 << 18)
 #define FUSE_HANDLE_KILLPRIV	(1 << 19)
 #define FUSE_POSIX_ACL		(1 << 20)
+#define FUSE_ABORT_ERROR	(1 << 21)
 
 /**
  * CUSE INIT request/reply flags
-- 
2.15.0