Thanks for comments.
Distro would also want to use the latest btrfs-progs on older kernel
since it will have latest fsck/send/receive fixes, better UI
and updated man pages.
btrfs-progs which claim backward kernel compatible and it shouldn't
fail on the below cmd when the btrfs-progs is upgraded.
mkfs.btrfs /dev/sda && mount /dev/sda /btrfs
but it does in some test cases.
A warning is unnecessary IMO. Imagine user who upgrade progs for
better doc/UI and have no intention to upgrade the kernel, gets a
Warning!. If user does not upgrade kernel its a fair assumption
that they don't need/not-looking for latest kernel features. (What
did I miss ?).
Next.
For users looking to have a disk-layout which is compatible with
older kernels (and may not be a running kernel), then with the
current patch set its quite possible to do something like below,
mkfs.btrfs -O as-per-kernel=3.2
mkfs.btrfs -O as-per-kernel=4.0
mkfs.btrfs -O as-per-kernel=x.x (anything)
And only those features that are supported until version x.x
(mainline) will be enabled by default unless user want to over
default totally by using -O <feature>.
Thanks, Anand
Anand Jain wrote:
Btrfs-progs is a tool for the btrfs kernel and we hope latest btrfs-progs
be compatible w any set of older/newer kernels.
So far mkfs.btrfs and btrfs-convert sets the default features, for eg,
skinny-metadata even if the running kernel does not supports it, and
so the mount fails on the running.
Here in this set of patches will make sure the progs understands the
kernel supported features.
So in this patch, checks if sysfs tells whether the feature is
supported if not, then it will relay on static kernel version which
provided that feature (skinny-metadata here in this example), next
if for some reason the running kernel does not provide the kernel
version, then it will fall back to the original method to enable
the feature with a hope that kernel will support it.
Also the last patch adds a warning when we fail to read either
sysfs features or the running kernel version.
With this I hope all the concerns from the review comments are
addressed.
Anand Jain (5):
btrfs-progs: introduce framework to check kernel supported features
btrfs-progs: add framework to check features supported by sysfs
btrfs-progs: kernel based default features for mkfs
btrfs-progs: kernel based default features for btrfs-convert
btrfs-progs: add warning when we fail to read sysfs or kernel version
btrfs-convert.c | 18 ++++++-
mkfs.c | 22 ++++++++-
utils.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
utils.h | 2 +
4 files changed, 173 insertions(+), 15 deletions(-)
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