GenDiskBuilder docs use the wrong block-size limit

The docs for GenDiskBuilder::logical_block_size and physical_block_size say the block size must be between 512 and 4096 bytes. The shared validate_block_size helper actually accepts powers of two up to PAGE_SIZE.

linux/rust/kernel/block/mq/gen_disk.rs

Lines 53 to 86 in 7059bdf

    
               /// Validate block size by verifying that it is between 512 and `PAGE_SIZE`, 
        
               /// and that it is a power of two. 
        
               pub fn validate_block_size(size: u32) -> Result { 
        
                   if !(512..=bindings::PAGE_SIZE as u32).contains(&size) || !size.is_power_of_two() { 
        
                       Err(error::code::EINVAL) 
        
                   } else { 
        
                       Ok(()) 
        
                   } 
        
               } 
        
               /// Set the logical block size of the device to be built. 
        
               /// 
        
               /// This method will check that block size is a power of two and between 512 
        
               /// and 4096. If not, an error is returned and the block size is not set. 
        
               /// 
        
               /// This is the smallest unit the storage device can address. It is 
        
               /// typically 4096 bytes. 
        
               pub fn logical_block_size(mut self, block_size: u32) -> Result<Self> { 
        
                   Self::validate_block_size(block_size)?; 
        
                   self.logical_block_size = block_size; 
        
                   Ok(self) 
        
               } 
        
               /// Set the physical block size of the device to be built. 
        
               /// 
        
               /// This method will check that block size is a power of two and between 512 
        
               /// and 4096. If not, an error is returned and the block size is not set. 
        
               /// 
        
               /// This is the smallest unit a physical storage device can write 
        
               /// atomically. It is usually the same as the logical block size but may be 
        
               /// bigger. One example is SATA drives with 4096 byte physical block size 
        
               /// that expose a 512 byte logical block size to the operating system. 
        
               pub fn physical_block_size(mut self, block_size: u32) -> Result<Self> { 
        
                   Self::validate_block_size(block_size)?;

On configurations with a larger page size, the documented limit is therefore too low.

Would a small patch updating both comments to use PAGE_SIZE be welcome? I can prepare it.

@metaspace

Yeah, that seems like an oversight, but pinging the maintainers...

Cc: @metaspace @fbq

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GenDiskBuilder docs use the wrong block-size limit #1245

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	/// Validate block size by verifying that it is between 512 and `PAGE_SIZE`,
	/// and that it is a power of two.
	pub fn validate_block_size(size: u32) -> Result {
	if !(512..=bindings::PAGE_SIZE as u32).contains(&size) \|\| !size.is_power_of_two() {
	Err(error::code::EINVAL)
	} else {
	Ok(())
	}
	}

	/// Set the logical block size of the device to be built.
	///
	/// This method will check that block size is a power of two and between 512
	/// and 4096. If not, an error is returned and the block size is not set.
	///
	/// This is the smallest unit the storage device can address. It is
	/// typically 4096 bytes.
	pub fn logical_block_size(mut self, block_size: u32) -> Result<Self> {
	Self::validate_block_size(block_size)?;
	self.logical_block_size = block_size;
	Ok(self)
	}

	/// Set the physical block size of the device to be built.
	///
	/// This method will check that block size is a power of two and between 512
	/// and 4096. If not, an error is returned and the block size is not set.
	///
	/// This is the smallest unit a physical storage device can write
	/// atomically. It is usually the same as the logical block size but may be
	/// bigger. One example is SATA drives with 4096 byte physical block size
	/// that expose a 512 byte logical block size to the operating system.
	pub fn physical_block_size(mut self, block_size: u32) -> Result<Self> {
	Self::validate_block_size(block_size)?;

GenDiskBuilder docs use the wrong block-size limit #1245

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ojeda commented on Jul 16, 2026

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