[PATCH v4 1/3] configfs: Restore the kernel v5.13 text attribute write behavior

Bart Van Assche
2021-08-05T04:35:19Z

Instead of appending new text attribute data at the offset specified by the
write() system call, only pass the newly written data to the .store()
callback.

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>
Reported-by: Bodo Stroesser <bostroesser@gmail.com>
Tested-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
fs/configfs/file.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 5a0be9985bae..0ad32150611e 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -177,28 +177,22 @@ static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
return retval;
}

-/* Fill [buffer, buffer + pos) with data coming from @from. */
-static int fill_write_buffer(struct configfs_buffer *buffer, loff_t pos,
+/* Fill @buffer with data coming from @from. */
+static int fill_write_buffer(struct configfs_buffer *buffer,
struct iov_iter *from)
{
- loff_t to_copy;
int copied;
- u8 *to;

if (!buffer->page)
buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
if (!buffer->page)
return -ENOMEM;

- to_copy = SIMPLE_ATTR_SIZE - 1 - pos;
- if (to_copy <= 0)
- return 0;
- to = buffer->page + pos;
- copied = copy_from_iter(to, to_copy, from);
+ copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
buffer->needs_read_fill = 1;
/* if buf is assumed to contain a string, terminate it by \0,
* so e.g. sscanf() can scan the string easily */
- to[copied] = 0;
+ buffer->page[copied] = 0;
return copied ? : -EFAULT;
}

@@ -227,10 +221,10 @@ 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;

mutex_lock(&buffer->mutex);
- len = fill_write_buffer(buffer, iocb->ki_pos, from);
+ len = fill_write_buffer(buffer, from);
if (len > 0)
len = flush_write_buffer(file, buffer, len);
if (len > 0)