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Howlett" , "Alice Ryhl" , "Anna-Maria Behnsen" , "Benno Lossin" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Boqun Feng" , "Danilo Krummrich" , "FUJITA Tomonori" , "Frederic Weisbecker" , "Gary Guo" , "Jens Axboe" , "John Stultz" , "Lorenzo Stoakes" , "Lyude Paul" , "Miguel Ojeda" , "Stephen Boyd" , "Thomas Gleixner" , "Trevor Gross" X-Mailer: aerc 0.21.0 References: <20260609-rnull-v6-19-rc5-send-v2-0-82c7404542e2@kernel.org> <20260609-rnull-v6-19-rc5-send-v2-23-82c7404542e2@kernel.org> In-Reply-To: <20260609-rnull-v6-19-rc5-send-v2-23-82c7404542e2@kernel.org> On Tue Jun 9, 2026 at 9:08 PM CEST, Andreas Hindborg wrote: > Add support for discard operations to the rnull block driver: > - Add discard module parameter and configfs attribute. > - Set max_hw_discard_sectors when discard is enabled. > - Add sector occupancy tracking. > - Add discard handling that frees sectors and removes empty pages. > - Discard operations require memory backing to function. > > The discard feature uses a bitmap to track which sectors in each page are > occupied, allowing cleanup of pages when they are empty. > > Signed-off-by: Andreas Hindborg > --- > drivers/block/rnull/configfs.rs | 15 +++++ > drivers/block/rnull/rnull.rs | 120 ++++++++++++++++++++++++++++++++++= +----- > 2 files changed, 121 insertions(+), 14 deletions(-) > > diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/config= fs.rs > index 2f3fa81ea121..e47399cd45a4 100644 > --- a/drivers/block/rnull/configfs.rs > +++ b/drivers/block/rnull/configfs.rs ... > } > }) > ); > + > +configfs_attribute!(DeviceConfig, 10, > + show: |this, page| show_field(this.data.lock().discard, page), > + store: |this, page| store_with_power_check(this, page, |data, page| = { > + if !data.memory_backed { > + return Err(EINVAL); > + } > + data.discard =3D kstrtobool_bytes(page)?; > + Ok(()) > + }) > +); Should it be ok to set 'discard' to 0 if 'emory_backed' is not set? In the C null_blk driver, 'discard' defaults to 0 if 'memory_backed' is not= set, it is also ignored (and defaulted to 0) if 'zoned' is enabled. Best regards, Malte