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Subject[PATCH 2/4] configfs: Fix writing at a non-zero offset
Date
Store data at the right offset when writing with a non-zero offset. I think
this patch fixes behavior introduced in the initial configfs commit. From a
source code comment in the initial configfs commit: "There is no easy way
for us to know if userspace is only doing a partial write, so we don't
support them."

Cc: Bodo Stroesser <bostroesser@gmail.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Yanko Kaneti <yaneti@declera.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
fs/configfs/file.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 8121bb1b2121..3b2ddc2e5d42 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -226,14 +226,16 @@ static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
- ssize_t len;
+ int len, written = 0;

mutex_lock(&buffer->mutex);
len = fill_write_buffer(buffer, iocb->ki_pos, from);
if (len > 0)
- len = flush_write_buffer(file, buffer, len);
- if (len > 0)
- iocb->ki_pos += len;
+ written = flush_write_buffer(file, buffer, iocb->ki_pos + len);
+ if (written > 0) {
+ len = max_t(int, 0, written - iocb->ki_pos);
+ iocb->ki_pos = written;
+ }
mutex_unlock(&buffer->mutex);
return len;
}
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