include/linux/writeback.h

Source file repositories/reference/linux-study-clean/include/linux/writeback.h

File Facts

System
Linux kernel
Corpus path
include/linux/writeback.h
Extension
.h
Size
12126 bytes
Lines
379
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct writeback_control {
	/* public fields that can be set and/or consumed by the caller: */
	long nr_to_write;		/* Write this many pages, and decrement
					   this for each page written */
	long pages_skipped;		/* Pages which were not written */

	/*
	 * For a_ops->writepages(): if start or end are non-zero then this is
	 * a hint that the filesystem need only write out the pages inside that
	 * byterange.  The byte at `end' is included in the writeout request.
	 */
	loff_t range_start;
	loff_t range_end;

	enum writeback_sync_modes sync_mode;

	unsigned for_kupdate:1;		/* A kupdate writeback */
	unsigned for_background:1;	/* A background writeback */
	unsigned tagged_writepages:1;	/* tag-and-write to avoid livelock */
	unsigned range_cyclic:1;	/* range_start is cyclic */
	unsigned for_sync:1;		/* sync(2) WB_SYNC_ALL writeback */
	unsigned unpinned_netfs_wb:1;	/* Cleared I_PINNING_NETFS_WB */

	/*
	 * When writeback IOs are bounced through async layers, only the
	 * initial synchronous phase should be accounted towards inode
	 * cgroup ownership arbitration to avoid confusion.  Later stages
	 * can set the following flag to disable the accounting.
	 */
	unsigned no_cgroup_owner:1;

	/* internal fields used by the ->writepages implementation: */
	struct folio_batch fbatch;
	pgoff_t index;
	int saved_err;

#ifdef CONFIG_CGROUP_WRITEBACK
	struct bdi_writeback *wb;	/* wb this writeback is issued under */
	struct inode *inode;		/* inode being written out */

	/* foreign inode detection, see wbc_detach_inode() */
	int wb_id;			/* current wb id */
	int wb_lcand_id;		/* last foreign candidate wb id */
	int wb_tcand_id;		/* this foreign candidate wb id */
	size_t wb_bytes;		/* bytes written by current wb */
	size_t wb_lcand_bytes;		/* bytes written by last candidate */
	size_t wb_tcand_bytes;		/* bytes written by this candidate */
#endif
};

static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
{
	blk_opf_t flags = 0;

	if (wbc->sync_mode == WB_SYNC_ALL)
		flags |= REQ_SYNC;
	else if (wbc->for_kupdate || wbc->for_background)
		flags |= REQ_BACKGROUND;

	return flags;
}

#ifdef CONFIG_CGROUP_WRITEBACK
#define wbc_blkcg_css(wbc) \
	((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css)
#else
#define wbc_blkcg_css(wbc)		(blkcg_root_css)
#endif /* CONFIG_CGROUP_WRITEBACK */

/*
 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
 * and are measured against each other in.  There always is one global
 * domain, global_wb_domain, that every wb in the system is a member of.
 * This allows measuring the relative bandwidth of each wb to distribute
 * dirtyable memory accordingly.
 */
struct wb_domain {
	spinlock_t lock;

	/*
	 * Scale the writeback cache size proportional to the relative
	 * writeout speed.
	 *
	 * We do this by keeping a floating proportion between BDIs, based
	 * on page writeback completions [end_page_writeback()]. Those
	 * devices that write out pages fastest will get the larger share,
	 * while the slower will get a smaller share.
	 *
	 * We use page writeout completions because we are interested in
	 * getting rid of dirty pages. Having them written out is the

Annotation

Implementation Notes