On Feb 11, 2014, at 11:43 AM, Theodore Ts'o <tytso@xxxxxxx> wrote:
> Based on the comments raised on the list, here is a revised version of
> the proposed ZBC kernel interface.
>
> Changes from the last version:
>
> 1) Aligned ZBC_FLAG values to be aligned with the ZBC specification to
> simplify implementations
> 2) Aligned the free_sector_criteria values to be mostly aligned with the ZBC
> specification
> 3) Clarified the behaviour of blkdev_query_zones()
> 4) Added an ioctl interface to expose this functionality to userspace
> 5) Removed the proposed simplified data variant
>
> Please let me know what you think!
Should ZBCRESETZONE take a length or number of zones to reset?
Cheers, Andreas
> /*
> * Note: this structure is 24 bytes. Using 256 MB zones, an 8TB drive
> * will have 32,768 zones. That means if we tried to use a contiguous
> * array we would need to allocate 768k of contiguous, non-swappable
> * kernel memory. (Boo, hiss.)
> *
> * This large enough that it would be painful to hang an array off the
> * block_device structure. So we will define a function
> * blkdev_query_zones() to selectively return information for some
> * number of zones.
> *
> * It is anticipated that the block device driver will store this
> * information in a compressed form, and that z_checkpoint_offset will
> * not be dynamically tracked. That is, the checkpoint offset will,
> * if non-zero, indicates that drive suffered a power fail event, and
> * the file system or userspace process may need to implement recovery
> * procedures. Once the file system or userspace process writes to an
> * SMR band, the checkpoint offset will be cleared and future queries
> * for the SMR band will return the checkpoint offset == write_ptr.
> */
> struct zone_status {
> sector_t z_start;
> __u32 z_length;
> __u32 z_write_ptr_offset; /* offset */
> __u32 z_checkpoint_offset; /* offset */
> __u32 z_flags; /* full, ro, offline, reset_requested */
> };
>
> #define Z_FLAG_RESET_REQUESTED 0x0001
> #define Z_FLAGS_OFFLINE 0x0002
> #define Z_FLAGS_RO 0x0004
> #define Z_FLAGS_FULL 0x0008
>
> #define Z_FLAG_TYPE_MASK 0x0F00
> #define Z_FLAG_TYPE_CONVENTIONAL 0x0100
> #define Z_FLAG_TYPE_SEQUENTIAL 0x0200
>
>
> /*
> * Query the block_device bdev for information about the zones
> * starting at start_sector that match the criteria specified by
> * free_sectors_criteria. Zone status information for at most
> * max_zones will be placed into the memory array ret_zones (which is
> * allocated by the caller, not by the blkdev_query_zones function),
> * in ascending LBA order. The return value will be a kernel error
> * code if negative, or the number of zones actually returned if
> * non-nonegative.
> *
> * If free_sectors_criteria is positive, then return zones that have
> * at least that many sectors available to be written. If it is zero,
> * then match all zones. If free_sectors_criteria is negative, then
> * return the zones that match the following criteria:
> *
> * -1 Match all full zones
> * -2 Match all open zones
> * (the zone has at least one written sector and is not full)
> * -3 Match all free zones
> * (the zone has no written sectors)
> * -4 Match all read-only zones
> * -5 Match all offline zones
> * -6 Match all zones where the write ptr != the checkpoint ptr
> *
> * The negative values are taken from Table 4 of 14-010r1, with the
> * exception of -6, which is not in the draft spec --- but IMHO should
> * be :-) It is anticipated, though, that the kernel will keep this
> * info in in memory and so will handle matching zones which meet
> * these criteria itself, without needing to issue a ZBC command for
> * each call to blkdev_query_zones().
> */
> extern int blkdev_query_zones(struct block_device *bdev,
> sector_t start_sector,
> int free_sectors_criteria,
> int max_zones,
> struct zone_status *ret_zones);
>
> /*
> * Reset the write pointer for a sequential write zone.
> *
> * Returns -EINVAL if the start_sector is not the beginning of a
> * sequential write zone.
> */
> extern int blkdev_reset_zone_ptr(struct block_dev *bdev,
> sector_t start_sector);
>
>
> /* ioctl interface */
>
> ZBCQUERY
> u64 starting_lba /* IN */
> u32 criteria /* IN */
> u32 *num_zones /* IN/OUT */
> struct zone_status *ptr /* OUT */
>
> ZBCRESETZONE
> u64 starting_lba
>
>
> --
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Cheers, Andreas
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