From e77751aad1facc4973613a11e2ad98ee4bbb04e1 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Fri, 27 Dec 2013 21:11:50 +0800 Subject: [PATCH] Btrfs: fix the wrong nocow range check The following warning message was outputed when running the 274th case of xfstests with nodatacow option: BUG: Bad page state in process kswapd0 pfn:1c66f page:ffffea0000636848 count:0 mapcount:0 mapping:(null) index:0x78000 page flags: 0x1000000000100a(error|uptodate|private_2) It is because the check of nocow range was wrong, we should compare the start and end position of the extent with the write position to verify if the write position was in the extent, but the current code just used the start postion to do the check, so we got the wrong extent and told the caller that it was a nocow write. And then when we write back the dirty pages, we found we should cow the extent, but at that time, there was no space in the fs, we had to the error flag for the page. When someone reclaimed that page, the above warning outputed. Fix it. Reported-by: Tsutomu Itoh Signed-off-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/inode.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 8e45fdcdbd8e..ffb23e506762 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6503,6 +6503,7 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len, int slot; int found_type; bool nocow = (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW); + path = btrfs_alloc_path(); if (!path) return -ENOMEM; @@ -6546,6 +6547,10 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len, if (!nocow && found_type == BTRFS_FILE_EXTENT_REG) goto out; + extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi); + if (extent_end <= offset) + goto out; + disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi); if (disk_bytenr == 0) goto out; @@ -6563,8 +6568,6 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len, *ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi); } - extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi); - if (btrfs_extent_readonly(root, disk_bytenr)) goto out; btrfs_release_path(path); -- 2.20.1