Commit 3ad216ee authored Nov 14, 2020 by David Howells Committed by Linus Torvalds Nov 14, 2020

afs: Fix afs_write_end() when called with copied == 0 [ver #3]



When afs_write_end() is called with copied == 0, it tries to set the
dirty region, but there's no way to actually encode a 0-length region in
the encoding in page->private.

"0,0", for example, indicates a 1-byte region at offset 0.  The maths
miscalculates this and sets it incorrectly.

Fix it to just do nothing but unlock and put the page in this case.  We
don't actually need to mark the page dirty as nothing presumably
changed.

Fixes: 65dd2d60 ("afs: Alter dirty range encoding in page->private")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f01c30de

fs/afs/write.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -169,11 +169,14 @@ int afs_write_end(struct file file, struct address_space mapping,
		unsigned int f, from = pos & (PAGE_SIZE - 1);
		unsigned int t, to = from + copied;
		loff_t i_size, maybe_i_size;
		int ret;
		int ret = 0;

		_enter("{%llx:%llu},{%lx}",
		vnode->fid.vid, vnode->fid.vnode, page->index);

		if (copied == 0)
		goto out;

		maybe_i_size = pos + copied;

		i_size = i_size_read(&vnode->vfs_inode);

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