From 4bcbb33255131adbe481c0467df26d654ce3bc78 Mon Sep 17 00:00:00 2001 From: Shilong Wang <wangshilong1991@gmail.com> Date: Tue, 7 Oct 2014 18:44:35 -0400 Subject: [PATCH] Btrfs: fix incorrect compression ratio detection Steps to reproduce: # mkfs.btrfs -f /dev/sdb # mount -t btrfs /dev/sdb /mnt -o compress=lzo # dd if=/dev/zero of=/mnt/data bs=$((33*4096)) count=1 after previous steps, inode will be detected as bad compression ratio, and NOCOMPRESS flag will be set for that inode. Reason is that compress have a max limit pages every time(128K), if a 132k write in, it will be splitted into two write(128k+4k), this bug is a leftover for commit 68bb462d42a(Btrfs: don't compress for a small write) Fix this problem by checking every time before compression, if it is a small write(<=blocksize), we bail out and fall into nocompression directly. Signed-off-by: Wang Shilong <wangshilong1991@gmail.com> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Chris Mason <clm@fb.com> --- fs/btrfs/inode.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 6fed30c3f9ce..793e033cbd17 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -411,14 +411,6 @@ static noinline int compress_file_range(struct inode *inode, (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size)) btrfs_add_inode_defrag(NULL, inode); - /* - * skip compression for a small file range(<=blocksize) that - * isn't an inline extent, since it dosen't save disk space at all. - */ - if ((end - start + 1) <= blocksize && - (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size)) - goto cleanup_and_bail_uncompressed; - actual_end = min_t(u64, isize, end + 1); again: will_compress = 0; @@ -440,6 +432,14 @@ static noinline int compress_file_range(struct inode *inode, total_compressed = actual_end - start; + /* + * skip compression for a small file range(<=blocksize) that + * isn't an inline extent, since it dosen't save disk space at all. + */ + if (total_compressed <= blocksize && + (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size)) + goto cleanup_and_bail_uncompressed; + /* we want to make sure that amount of ram required to uncompress * an extent is reasonable, so we limit the total size in ram * of a compressed extent to 128k. This is a crucial number -- 2.30.9