From dd22f551ac0ad366f92f601835f6623b83adc331 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Wed, 7 Jan 2015 18:05:34 +0200 Subject: block: Change direct_access calling convention In order to support accesses to larger chunks of memory, pass in a 'size' parameter (counted in bytes), and return the amount available at that address. Add a new helper function, bdev_direct_access(), to handle common functionality including partition handling, checking the length requested is positive, checking for the sector being page-aligned, and checking the length of the request does not pass the end of the partition. Signed-off-by: Matthew Wilcox Reviewed-by: Jan Kara Reviewed-by: Boaz Harrosh Signed-off-by: Jens Axboe --- Documentation/filesystems/xip.txt | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'Documentation/filesystems') diff --git a/Documentation/filesystems/xip.txt b/Documentation/filesystems/xip.txt index 0466ee569278..b77472949ede 100644 --- a/Documentation/filesystems/xip.txt +++ b/Documentation/filesystems/xip.txt @@ -28,12 +28,15 @@ Implementation Execute-in-place is implemented in three steps: block device operation, address space operation, and file operations. -A block device operation named direct_access is used to retrieve a -reference (pointer) to a block on-disk. The reference is supposed to be -cpu-addressable, physical address and remain valid until the release operation -is performed. A struct block_device reference is used to address the device, -and a sector_t argument is used to identify the individual block. As an -alternative, memory technology devices can be used for this. +A block device operation named direct_access is used to translate the +block device sector number to a page frame number (pfn) that identifies +the physical page for the memory. It also returns a kernel virtual +address that can be used to access the memory. + +The direct_access method takes a 'size' parameter that indicates the +number of bytes being requested. The function should return the number +of bytes that can be contiguously accessed at that offset. It may also +return a negative errno if an error occurs. The block device operation is optional, these block devices support it as of today: -- cgit v1.2.3