Mkfs from latest btrfs-progs will enable latest default features,
and if the kernel is down-rev and does not support a latest default
feature then mount fails, as expected.

This patch disables default features based on the running kernel.

Signed-off-by: Anand Jain <[email protected]>
---
v2: Check if sysfs tells what features are supported

 mkfs.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mkfs.c b/mkfs.c
index a5802f7..4f46ad9 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -1357,10 +1357,24 @@ int main(int ac, char **av)
        int dev_cnt = 0;
        int saved_optind;
        char fs_uuid[BTRFS_UUID_UNPARSED_SIZE] = { 0 };
-       u64 features = BTRFS_MKFS_DEFAULT_FEATURES;
+       u64 features;
        struct mkfs_allocation allocation = { 0 };
        struct btrfs_mkfs_config mkfs_cfg;
 
+       /*
+        * If kernel could tell supported features by sysfs then use it,
+        * if not, then set it by static kernel version, if the this also
+        * fails then default to the progs default, which is set as per
+        * BTRFS_MKFS_DEFAULT_FEATURES
+        */
+       if (btrfs_features_allowed_by_sysfs(&features))
+               features = btrfs_features_allowed_by_kernel();
+
+       if (features)
+               features &= BTRFS_MKFS_DEFAULT_FEATURES;
+       else
+               features = BTRFS_MKFS_DEFAULT_FEATURES;
+
        while(1) {
                int c;
                static const struct option long_options[] = {
-- 
2.6.2

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