fs/xfs/xfs_buf_item.c

Source file repositories/reference/linux-study-clean/fs/xfs/xfs_buf_item.c

File Facts

System
Linux kernel
Corpus path
fs/xfs/xfs_buf_item.c
Extension
.c
Size
31636 bytes
Lines
1087
Domain
Core OS
Bucket
VFS And Filesystem Core
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

if (map_size > XFS_BLF_DATAMAP_SIZE) {
			xfs_buf_item_free_format(bip);
			kmem_cache_free(xfs_buf_item_cache, bip);
			xfs_err(mp,
	"buffer item dirty bitmap (%u uints) too small to reflect %u bytes!",
					map_size,
					BBTOB(bp->b_maps[i].bm_len));
			return -EFSCORRUPTED;
		}

		bip->bli_formats[i].blf_type = XFS_LI_BUF;
		bip->bli_formats[i].blf_blkno = bp->b_maps[i].bm_bn;
		bip->bli_formats[i].blf_len = bp->b_maps[i].bm_len;
		bip->bli_formats[i].blf_map_size = map_size;
	}

	bp->b_log_item = bip;
	xfs_buf_hold(bp);
	return 0;
}


/*
 * Mark bytes first through last inclusive as dirty in the buf
 * item's bitmap.
 */
static void
xfs_buf_item_log_segment(
	uint			first,
	uint			last,
	uint			*map)
{
	uint		first_bit;
	uint		last_bit;
	uint		bits_to_set;
	uint		bits_set;
	uint		word_num;
	uint		*wordp;
	uint		bit;
	uint		end_bit;
	uint		mask;

	ASSERT(first < XFS_BLF_DATAMAP_SIZE * XFS_BLF_CHUNK * NBWORD);
	ASSERT(last < XFS_BLF_DATAMAP_SIZE * XFS_BLF_CHUNK * NBWORD);

	/*
	 * Convert byte offsets to bit numbers.
	 */
	first_bit = first >> XFS_BLF_SHIFT;
	last_bit = last >> XFS_BLF_SHIFT;

	/*
	 * Calculate the total number of bits to be set.
	 */
	bits_to_set = last_bit - first_bit + 1;

	/*
	 * Get a pointer to the first word in the bitmap
	 * to set a bit in.
	 */
	word_num = first_bit >> BIT_TO_WORD_SHIFT;
	wordp = &map[word_num];

	/*
	 * Calculate the starting bit in the first word.
	 */
	bit = first_bit & (uint)(NBWORD - 1);

	/*
	 * First set any bits in the first word of our range.
	 * If it starts at bit 0 of the word, it will be
	 * set below rather than here.  That is what the variable
	 * bit tells us. The variable bits_set tracks the number
	 * of bits that have been set so far.  End_bit is the number
	 * of the last bit to be set in this word plus one.
	 */
	if (bit) {
		end_bit = min(bit + bits_to_set, (uint)NBWORD);
		mask = ((1U << (end_bit - bit)) - 1) << bit;
		*wordp |= mask;
		wordp++;
		bits_set = end_bit - bit;
	} else {
		bits_set = 0;
	}

	/*
	 * Now set bits a whole word at a time that are between
	 * first_bit and last_bit.
	 */

Annotation

Implementation Notes