clio

Client objects implement io operations and cache pages. More...

Modules
	cl_object
	cl_page
	cl_lock
	cl_io
	cl_page_list
	Page list used to perform collective operations on a group of pages.
	cl_req
	cl_env
	lu_env handling for a client.
Data Structures
struct	cl_device_operations
	Operations for each data device in the client stack. More...
struct	cl_device
	Device in the client stack. More...
struct	cache_stats
	Stats for a generic cache (similar to inode, lu_object, etc. More...
struct	cl_site
	Client-side site. More...
helpers
Type conversion and accessory functions.
void	cl_page_slice_add (struct cl_page *page, struct cl_page_slice *slice, struct cl_object *obj, const struct cl_page_operations *ops)
	Adds page slice to the compound page.
void	cl_lock_slice_add (struct cl_lock *lock, struct cl_lock_slice *slice, struct cl_object *obj, const struct cl_lock_operations *ops)
	Adds lock slice to the compound lock.
void	cl_io_slice_add (struct cl_io *io, struct cl_io_slice *slice, struct cl_object *obj, const struct cl_io_operations *ops)
	Adds io slice to the cl_io.
void	cl_req_slice_add (struct cl_req *req, struct cl_req_slice *slice, struct cl_device *dev, const struct cl_req_operations *ops)
	Adds request slice to the compound request.
Defines
#define	pgoff_t   unsigned long
#define	CL_PAGE_EOF   ((pgoff_t)~0ull)
Functions
void	cache_stats_init (struct cache_stats *cs, const char *name)
	These are not exported so far.
int	cache_stats_print (const struct cache_stats *cs, char *page, int count, int header)
int	cl_site_init (struct cl_site *s, struct cl_device *top)
	Initialize client site.
void	cl_site_fini (struct cl_site *s)
	Finalize client site.
void	cl_stack_fini (const struct lu_env *env, struct cl_device *cl)
	Finalize device stack by calling lu_stack_fini().
int	cl_site_stats_print (const struct cl_site *s, char *page, int count)
	Output client site statistical counters into a buffer.
void	cl_attr2lvb (struct ost_lvb *lvb, const struct cl_attr *attr)
	Converts struct cl_attr to struct ost_lvb.
void	cl_lvb2attr (struct cl_attr *attr, const struct ost_lvb *lvb)
	Converts struct ost_lvb to struct cl_attr.
cl_device *	cl_type_setup (const struct lu_env *env, struct lu_site *site, struct lu_device_type *ldt, struct lu_device *next)

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Detailed Description

Client objects implement io operations and cache pages.

Examples: lov and osc are implementations of cl interface.

Big Theory Statement.

Layered objects.

Client implementation is based on the following data-types:

• cl_object

• cl_page

• cl_lock represents an extent lock on an object.

• cl_io represents high-level i/o activity such as whole read/write system call, or write-out of pages from under the lock being canceled. cl_io has sub-ios that can be stopped and resumed independently, thus achieving high degree of transfer parallelism. Single cl_io can be advanced forward by the multiple threads (although in the most usual case of read/write system call it is associated with the single user thread, that issued the system call).

• cl_req represents a collection of pages for a transfer. cl_req is constructed by req-forming engine that tries to saturate transport with large and continuous transfers.

Terminology

• to avoid confusion high-level I/O operation like read or write system call is referred to as "an io", whereas low-level I/O operation, like RPC, is referred to as "a transfer"

• "generic code" means generic (not file system specific) code in the hosting environment. "cl-code" means code (mostly in cl_*.c files) that is not layer specific.

Locking.

• i_mutex
  • PG_locked
    • cl_object_header::coh_page_guard
    • cl_object_header::coh_lock_guard
    • lu_site::ls_guard

See the top comment in cl_object.c for the description of overall locking and reference-counting design.

See comments below for the description of i/o, page, and dlm-locking design.

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Function Documentation

void cl_attr2lvb	(	struct ost_lvb *	lvb,
		const struct cl_attr *	attr
	)

Converts struct cl_attr to struct ost_lvb.

See also:

cl_lvb2attr

void cl_io_slice_add	(	struct cl_io *	io,
		struct cl_io_slice *	slice,
		struct cl_object *	obj,
		const struct cl_io_operations *	ops
	)

Adds io slice to the cl_io.

This is called by cl_object_operations::coo_io_init() methods to add a per-layer state to the io. New state is added at the end of cl_io::ci_layers list, that is, it is at the bottom of the stack.

See also:

cl_lock_slice_add(), cl_req_slice_add(), cl_page_slice_add()

void cl_lock_slice_add	(	struct cl_lock *	lock,
		struct cl_lock_slice *	slice,
		struct cl_object *	obj,
		const struct cl_lock_operations *	ops
	)

Adds lock slice to the compound lock.

This is called by cl_object_operations::coo_lock_init() methods to add a per-layer state to the lock. New state is added at the end of cl_lock::cll_layers list, that is, it is at the bottom of the stack.

See also:

cl_req_slice_add(), cl_page_slice_add(), cl_io_slice_add()

void cl_lvb2attr	(	struct cl_attr *	attr,
		const struct ost_lvb *	lvb
	)

Converts struct ost_lvb to struct cl_attr.

See also:

cl_attr2lvb

void cl_page_slice_add	(	struct cl_page *	page,
		struct cl_page_slice *	slice,
		struct cl_object *	obj,
		const struct cl_page_operations *	ops
	)

Adds page slice to the compound page.

This is called by cl_object_operations::coo_page_init() methods to add a per-layer state to the page. New state is added at the end of cl_page::cp_layers list, that is, it is at the bottom of the stack.

See also:

cl_lock_slice_add(), cl_req_slice_add(), cl_io_slice_add()

void cl_req_slice_add	(	struct cl_req *	req,
		struct cl_req_slice *	slice,
		struct cl_device *	dev,
		const struct cl_req_operations *	ops
	)

Adds request slice to the compound request.

This is called by cl_device_operations::cdo_req_init() methods to add a per-layer state to the request. New state is added at the end of cl_req::crq_layers list, that is, it is at the bottom of the stack.

See also:

cl_lock_slice_add(), cl_page_slice_add(), cl_io_slice_add()

void cl_site_fini

(

struct cl_site *

s

)

Finalize client site.

Dual to cl_site_init().

int cl_site_init	(	struct cl_site *	s,
		struct cl_device *	d
	)

Initialize client site.

Perform common initialization (lu_site_init()), and initialize statistical counters. Also perform global initializations on the first call.

int cl_site_stats_print	(	const struct cl_site *	site,
		char *	page,
		int	count
	)

Output client site statistical counters into a buffer.

Suitable for ll_rd_*()-style functions.

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