From: Filipe Manana fdmanana@suse.com
commit b767c2fc787e992daeadfff40d61c05f66c82da0 upstream.
During defrag, at btrfs_defrag_file(), we have this loop that iterates over a file range in steps no larger than 256K subranges. If the range is too long, there's no way to interrupt it. So make the loop check in each iteration if there's signal pending, and if there is, break and return -AGAIN to userspace.
Before kernel 5.16, we used to allow defrag to be cancelled through a signal, but that was lost with commit 7b508037d4cac3 ("btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()").
This change adds back the possibility to cancel a defrag with a signal and keeps the same semantics, returning -EAGAIN to user space (and not the usually more expected -EINTR).
This is also motivated by a recent bug on 5.16 where defragging a 1 byte file resulted in iterating from file range 0 to (u64)-1, as hitting the bug triggered a too long loop, basically requiring one to reboot the machine, as it was not possible to cancel defrag.
Fixes: 7b508037d4cac3 ("btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()") CC: stable@vger.kernel.org # 5.16 Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/ioctl.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1520,6 +1520,11 @@ int btrfs_defrag_file(struct inode *inod /* The cluster size 256K should always be page aligned */ BUILD_BUG_ON(!IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
+ if (btrfs_defrag_cancelled(fs_info)) { + ret = -EAGAIN; + break; + } + /* We want the cluster end at page boundary when possible */ cluster_end = (((cur >> PAGE_SHIFT) + (SZ_256K >> PAGE_SHIFT)) << PAGE_SHIFT) - 1;