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SubjectRe: [REGRESSION] usb: gadget: f_fs: Allow scatter-gather buffers
Date
Hi John,

W dniu 08.05.2019 o 04:18, John Stultz pisze:
> Since commit 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather
> buffers"), I've been seeing trouble with adb transfers in Android on
> HiKey960, HiKey and now Dragonboard 845c.
>
> Sometimes things crash, but often the transfers just stop w/o any
> obvious error messages.
>

<snip>

>
> Andrzej: Do you have any ideas or suggestions on this? I'm happy to
> test or run any debug patches, if it would help narrow the issue down.
>

Can you please try the below patch?

One more thing to consider is "functionfs read size 512 > requested size 24,
splitting request into multiple reads." in your original report, but let's
try this first:

From f2b8f27cfa42cafe1f56d8abbe2c76fa0072e368 Mon Sep 17 00:00:00 2001
From: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Date: Wed, 8 May 2019 13:52:40 +0200
Subject: [PATCH] usb: gadget: Zero ffs_io_data

In some cases the "Allocate & copy" block in ffs_epfile_io() is not
executed. Consequently, in such a case ffs_alloc_buffer() is never called
and struct ffs_io_data is not initialized properly. This in turn leads to
problems when ffs_free_buffer() is called at the end of ffs_epfile_io().

This patch uses kzalloc() instead of kmalloc() in the aio case and memset()
in non-aio case to properly initialize struct ffs_io_data.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
drivers/usb/gadget/function/f_fs.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 47be961f1bf3..41d57ae8bc15 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1182,11 +1182,12 @@ static ssize_t ffs_epfile_write_iter(struct kiocb
*kiocb, struct iov_iter *from)
ENTER();

if (!is_sync_kiocb(kiocb)) {
- p = kmalloc(sizeof(io_data), GFP_KERNEL);
+ p = kzalloc(sizeof(io_data), GFP_KERNEL);
if (unlikely(!p))
return -ENOMEM;
p->aio = true;
} else {
+ memset(p, 0, sizeof(*p));
p->aio = false;
}

@@ -1218,11 +1219,12 @@ static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb,
struct iov_iter *to)
ENTER();

if (!is_sync_kiocb(kiocb)) {
- p = kmalloc(sizeof(io_data), GFP_KERNEL);
+ p = kzalloc(sizeof(io_data), GFP_KERNEL);
if (unlikely(!p))
return -ENOMEM;
p->aio = true;
} else {
+ memset(p, 0, sizeof(*p));
p->aio = false;
}

--
2.17.1
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