btrfs: Ensure btrfs_trim_fs can trim the whole filesystem

[BUG]
fstrim on some btrfs only trims the unallocated space, not trimming any
space in existing block groups.

[CAUSE]
Before fstrim_range passed to btrfs_trim_fs(), it gets truncated to
range [0, super->total_bytes).  So later btrfs_trim_fs() will only be
able to trim block groups in range [0, super->total_bytes).

While for btrfs, any bytenr aligned to sectorsize is valid, since btrfs
uses its logical address space, there is nothing limiting the location
where we put block groups.

For filesystem with frequent balance, it's quite easy to relocate all
block groups and bytenr of block groups will start beyond
super->total_bytes.

In that case, btrfs will not trim existing block groups.

[FIX]
Just remove the truncation in btrfs_ioctl_fitrim(), so btrfs_trim_fs()
can get the unmodified range, which is normally set to [0, U64_MAX].

Reported-by: Chris Murphy <lists@colorremedies.com>
Fixes: f4c697e6406d ("btrfs: return EINVAL if start > total_bytes in fitrim ioctl")
CC: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4905d13dee0a..a990a9045139 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -491,7 +491,6 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
 	struct fstrim_range range;
 	u64 minlen = ULLONG_MAX;
 	u64 num_devices = 0;
-	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
 	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -515,11 +514,15 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
 		return -EOPNOTSUPP;
 	if (copy_from_user(&range, arg, sizeof(range)))
 		return -EFAULT;
-	if (range.start > total_bytes ||
-	    range.len < fs_info->sb->s_blocksize)
+
+	/*
+	 * NOTE: Don't truncate the range using super->total_bytes.  Bytenr of
+	 * block group is in the logical address space, which can be any
+	 * sectorsize aligned bytenr in  the range [0, U64_MAX].
+	 */
+	if (range.len < fs_info->sb->s_blocksize)
 		return -EINVAL;
 
-	range.len = min(range.len, total_bytes - range.start);
 	range.minlen = max(range.minlen, minlen);
 	ret = btrfs_trim_fs(fs_info, &range);
 	if (ret < 0)