From 93a54bc4c28a125978cddbe2db9e347391e3522d Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Wed, 6 Apr 2011 15:11:44 -0400 Subject: [PATCH] Btrfs: check for duplicate iov_base's when doing dio reads Apparently it is ok to submit a read to an IDE device with the same target page for different offsets. This is what Windows does under qemu. The problem is under DIO we expect them to be different buffers for checksumming reasons, and so this sort of thing will result in checksum errors, when in reality the file is fine. So when reading, check to make sure that all iov bases are different, and if they aren't fall back to buffered mode, since that will work out right. Thanks, Signed-off-by: Josef Bacik --- fs/btrfs/inode.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 24310c9..00d59c6 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6207,6 +6207,7 @@ static ssize_t check_direct_IO(struct btrfs_root *root, int rw, struct kiocb *io unsigned long nr_segs) { int seg; + int i; size_t size; unsigned long addr; unsigned blocksize_mask = root->sectorsize - 1; @@ -6221,8 +6222,22 @@ static ssize_t check_direct_IO(struct btrfs_root *root, int rw, struct kiocb *io addr = (unsigned long)iov[seg].iov_base; size = iov[seg].iov_len; end += size; - if ((addr & blocksize_mask) || (size & blocksize_mask)) + if ((addr & blocksize_mask) || (size & blocksize_mask)) goto out; + + /* If this is a write we don't need to check anymore */ + if (rw & WRITE) + continue; + + /* + * Check to make sure we don't have duplicate iov_base's in this + * iovec, if so return EINVAL, otherwise we'll get csum errors + * when reading back. + */ + for (i = seg + 1; i < nr_segs; i++) { + if (iov[seg].iov_base == iov[i].iov_base) + goto out; + } } retval = 0; out: -- 2.7.4