Re: block: Don't invalidate pagecache for invalid falloc modes

[Mike Snitzer]

On Wed, Oct 11 2023 at  4:20P -0400,
Jens Axboe <axboe@xxxxxxxxx> wrote:

> On 10/11/23 2:12 PM, Sarthak Kukreti wrote:
> > Only call truncate_bdev_range() if the fallocate mode is
> > supported. This fixes a bug where data in the pagecache
> > could be invalidated if the fallocate() was called on the
> > block device with an invalid mode.
> 
> Fix looks fine, but would be nicer if we didn't have to duplicate the
> truncate_bdev_range() in each switch clause. Can we check this upfront
> instead?

No, if you look at the function (rather than just the patch in
isolation) we need to make the call for each case rather than collapse
to a single call at the front (that's the reason for this fix, because
otherwise the default: error case will invalidate the page cache too).

Just so you're aware, I also had this feedback that shaped the patch a
bit back in April:
https://listman.redhat.com/archives/dm-devel/2023-April/053986.html

> Also, please wrap commit messages at 72-74 chars.

Not seeing where the header should be wrapped.  You referring to the
Fixes: line?  I've never seen those wrapped.

Mike