From 31339acd07b4ba687906702085127895a56eb920 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Mon, 7 Mar 2011 11:10:24 -0500 Subject: [PATCH] Btrfs: deal with short returns from copy_from_user When copy_from_user is only able to copy some of the bytes we requested, we may end up creating a partially up to date page. To avoid garbage in the page, we need to treat a partial copy as a zero length copy. This makes the rest of the file_write code drop the page and retry the whole copy instead of marking the partially up to date page as dirty. Signed-off-by: Chris Mason cc: stable@kernel.org --- fs/btrfs/file.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 13664b315fe..ab22ca4f237 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -69,6 +69,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages, /* Flush processor's dcache for this page */ flush_dcache_page(page); + + /* + * if we get a partial write, we can end up with + * partially up to date pages. These add + * a lot of complexity, so make sure they don't + * happen by forcing this copy to be retried. + * + * The rest of the btrfs_file_write code will fall + * back to page at a time copies after we return 0. + */ + if (!PageUptodate(page) && copied < count) + copied = 0; + iov_iter_advance(i, copied); write_bytes -= copied; total_copied += copied; -- 2.39.2