From 259072b7a1c20f8612dcaa8e0e027004aa98f864 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Wed, 6 Jan 2016 22:42:35 +0000 Subject: [PATCH 2/2] Btrfs: fix fitrim discarding device area reserved for boot loader's use As of the 4.3 kernel release, the fitrim ioctl can now discard any region of a disk that is not allocated to any chunk/block group, including the first megabyte which is used for our primary superblock and by the boot loader (grub for example). Fix this by not allowing to trim/discard any region in the device starting with an offset not greater than min(alloc_start_mount_option, 1Mb), just as it was not possible before 4.3. A reproducer test case for xfstests follows. seq=`basename $0` seqres=$RESULT_DIR/$seq echo "QA output created by $seq" tmp=/tmp/$$ status=1 # failure is the default! trap "_cleanup; exit \$status" 0 1 2 3 15 _cleanup() { cd / rm -f $tmp.* } # get standard environment, filters and checks . ./common/rc . ./common/filter # real QA test starts here _need_to_be_root _supported_fs btrfs _supported_os Linux _require_scratch rm -f $seqres.full _scratch_mkfs >>$seqres.full 2>&1 # Write to the [0, 64Kb[ and [68Kb, 1Mb[ ranges of the device. These ranges are # reserved for a boot loader to use (GRUB for example) and btrfs should never # use them - neither for allocating metadata/data nor should trim/discard them. # The range [64Kb, 68Kb[ is used for the primary superblock of the filesystem. $XFS_IO_PROG -c "pwrite -S 0xfd 0 64K" $SCRATCH_DEV | _filter_xfs_io $XFS_IO_PROG -c "pwrite -S 0xfd 68K 956K" $SCRATCH_DEV | _filter_xfs_io # Now mount the filesystem and perform a fitrim against it. _scratch_mount _require_batched_discard $SCRATCH_MNT $FSTRIM_PROG $SCRATCH_MNT # Now unmount the filesystem and verify the content of the ranges was not # modified (no trim/discard happened on them). _scratch_unmount echo "Content of the ranges [0, 64Kb] and [68Kb, 1Mb[ after fitrim:" od -t x1 -N $((64 * 1024)) $SCRATCH_DEV od -t x1 -j $((68 * 1024)) -N $((956 * 1024)) $SCRATCH_DEV status=0 exit Reported-by: Vincent Petry Reported-by: Andrei Borzenkov Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109341 Fixes: 499f377f49f0 (btrfs: iterate over unused chunk space in FITRIM) Cc: stable@vger.kernel.org # 4.3+ Signed-off-by: Filipe Manana --- fs/btrfs/volumes.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index b816b3a2e118..96f8c827d563 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1208,6 +1208,15 @@ int find_free_dev_extent_start(struct btrfs_transaction *transaction, int ret; int slot; struct extent_buffer *l; + u64 min_search_start; + + /* + * We don't want to overwrite the superblock on the drive nor any area + * used by the boot loader (grub for example), so we make sure to start + * at an offset of at least 1MB. + */ + min_search_start = max(root->fs_info->alloc_start, 1024ull * 1024); + search_start = max(search_start, min_search_start); path = btrfs_alloc_path(); if (!path) @@ -1348,18 +1357,9 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans, struct btrfs_device *device, u64 num_bytes, u64 *start, u64 *len) { - struct btrfs_root *root = device->dev_root; - u64 search_start; - /* FIXME use last free of some kind */ - - /* - * we don't want to overwrite the superblock on the drive, - * so we make sure to start at an offset of at least 1MB - */ - search_start = max(root->fs_info->alloc_start, 1024ull * 1024); return find_free_dev_extent_start(trans->transaction, device, - num_bytes, search_start, start, len); + num_bytes, 0, start, len); } static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans, -- 2.5.0