On Mon, Jul 01, 2019 at 05:12:46AM +0000, Qu Wenruo wrote: > As btrfs(5) specified: > > Note > If nodatacow or nodatasum are enabled, compression is disabled. > > If NODATASUM or NODATACOW set, we should not compress the extent. > > Normally NODATACOW is detected properly in run_delalloc_range() so > compression won't happen for NODATACOW. > > However for NODATASUM we don't have any check, and it can cause > compressed extent without csum pretty easily, just by: > mkfs.btrfs -f $dev > mount $dev $mnt -o nodatasum > touch $mnt/foobar > mount -o remount,datasum,compress $mnt > xfs_io -f -c "pwrite 0 128K" $mnt/foobar > > And in fact, we have a bug report about corrupted compressed extent > without proper data checksum so even RAID1 can't recover the corruption. > (https://bugzilla.kernel.org/show_bug.cgi?id=199707) > > Running compression without proper checksum could cause more damage when > corruption happens, as compressed data could make the whole extent > unreadable, so there is no need to allow compression for > NODATACSUM. > > The fix will refactor the inode compression check into two parts: > - inode_can_compress() > As the hard requirement, checked at btrfs_run_delalloc_range(), so no > compression will happen for NODATASUM inode at all. > > - inode_need_compress() > As the soft requirement, checked at btrfs_run_delalloc_range() and > compress_file_range(). > > Reported-by: James Harvey <jamespharvey20@xxxxxxxxx> > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > --- > Changelog: > v2: > - Refactor inode_need_compress() into two functions > - Refactor inode_need_compress() to return bool > --- > fs/btrfs/inode.c | 38 ++++++++++++++++++++++++++++++++------ > 1 file changed, 32 insertions(+), 6 deletions(-) > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index a2aabdb85226..be1cabf35680 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -394,24 +394,49 @@ static noinline int add_async_extent(struct async_chunk *cow, > return 0; > } > > -static inline int inode_need_compress(struct inode *inode, u64 start, u64 end) > +/* > + * Check if the inode can accept compression. > + * > + * This checks for the hard requirement of compression, including CoW and > + * checksum requirement. > + */ > +static inline bool inode_can_compress(struct inode *inode) > +{ > + if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW || > + BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) > + return false; > + return true; > +} > + > +/* > + * Check if the inode need compression. > + * > + * This checks for the soft requirement of compression. > + */ > +static inline bool inode_need_compress(struct inode *inode, u64 start, u64 end) > { > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > > + if (!inode_can_compress(inode)) { > + WARN(IS_ENABLED(CONFIG_BTRFS_DEBUG), > + KERN_ERR "BTRFS: unexpected compression for ino %llu\n", > + btrfs_ino(BTRFS_I(inode))); > + return false; > + } > /* force compress */ > if (btrfs_test_opt(fs_info, FORCE_COMPRESS)) > - return 1; > + return true; > /* defrag ioctl */ > if (BTRFS_I(inode)->defrag_compress) > - return 1; > + return true; > /* bad compression ratios */ > if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS) > - return 0; > + return false; > if (btrfs_test_opt(fs_info, COMPRESS) || > BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS || > BTRFS_I(inode)->prop_compress) > return btrfs_compress_heuristic(inode, start, end); > - return 0; > + return false; > } > > static inline void inode_should_defrag(struct btrfs_inode *inode, > @@ -1630,7 +1655,8 @@ int btrfs_run_delalloc_range(struct inode *inode, struct page *locked_page, > } else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) { > ret = run_delalloc_nocow(inode, locked_page, start, end, > page_started, 0, nr_written); > - } else if (!inode_need_compress(inode, start, end)) { > + } else if (!inode_can_compress(inode) || > + !inode_need_compress(inode, start, end)) { Well, that's not excatly what I expected, but because this is an important fix I won't object now and add it to 5.3 queue.
