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configfs: don't set buffer_needs_fill to zero if show() returns error 

A confgifs attribute's show() callback is called once the first time
the user attempts to read from it. If it returns an error, that
error is returned to the user. However, the open file's
buffer_needs_fill is still set to zero and consecutive read() calls
will find an empty buffer that doesn't need filling and return 0 to
the user. This could give the user the wrong impression that the
attribute was read successfully.

Fix this by not setting buffer_needs_fill if show() returns an error,
making consecutive read() calls call show() again and either get an
error again or get data.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Tal Shorer 2016-07-01 12:28:57 +03:00 committed by Christoph Hellwig
parent ee40fb2948
commit 3dc3afadeb
1 changed files with 3 additions and 3 deletions
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6
fs/configfs/file.c
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@ -80,11 +80,11 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
count = attr->show(item, buffer->page);
buffer->needs_read_fill = 0;
BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
if (count >= 0)
if (count >= 0) {
buffer->needs_read_fill = 0;
buffer->count = count;
else
} else
ret = count;
return ret;
}