linux-kernel - [PATCH v2] usb: gadget: f_fs: Use stream

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Date:   Thu, 11 Nov 2021 17:45:56 +0530
From:   Pavankumar Kondeti <quic_pkondeti@...cinc.com>
To:     <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
CC:     Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Jens Axboe" <axboe@...nel.dk>, Jack Pham <jackp@...eaurora.org>,
        Peter Chen <peter.chen@....com>,
        Wesley Cheng <wcheng@...eaurora.org>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH v2] usb: gadget: f_fs: Use stream_open() for endpoint files

Function fs endpoint files does not have the notion of file position.
So switch to stream like functionality. This allows concurrent threads
to be blocked in the ffs read/write operations which use ffs_mutex_lock().
The ffs mutex lock deploys interruptible wait. Otherwise, threads are
blocking for the mutex lock in __fdget_pos(). For whatever reason, ff the
host does not send/receive data for longer time, hung task warnings
are observed.

Signed-off-by: Pavankumar Kondeti <quic_pkondeti@...cinc.com>
---
V2:
- Removed Change-Id tag

 drivers/usb/gadget/function/f_fs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index e20c19a..3c584da 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -614,7 +614,7 @@ static int ffs_ep0_open(struct inode *inode, struct file *file)
 	file->private_data = ffs;
 	ffs_data_opened(ffs);
 
-	return 0;
+	return stream_open(inode, file);
 }
 
 static int ffs_ep0_release(struct inode *inode, struct file *file)
@@ -1154,7 +1154,7 @@ ffs_epfile_open(struct inode *inode, struct file *file)
 	file->private_data = epfile;
 	ffs_data_opened(epfile->ffs);
 
-	return 0;
+	return stream_open(inode, file);
 }
 
 static int ffs_aio_cancel(struct kiocb *kiocb)
-- 
2.7.4