fs/xfs/libxfs/xfs_dir2_block.c

Source file repositories/reference/linux-study-clean/fs/xfs/libxfs/xfs_dir2_block.c

File Facts

System
Linux kernel
Corpus path
fs/xfs/libxfs/xfs_dir2_block.c
Extension
.c
Size
35950 bytes
Lines
1282
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 (be16_to_cpu(bf[0].length) >= len) {
			/*
			 * The biggest entry enough to avoid compaction.
			 */
			dup = (xfs_dir2_data_unused_t *)
			      ((char *)hdr + be16_to_cpu(bf[0].offset));
			goto out;
		}

		/*
		 * Will need to compact to make this work.
		 * Tag just before the first leaf entry.
		 */
		*compact = 1;
		tagp = (__be16 *)blp - 1;

		/* Data object just before the first leaf entry.  */
		dup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));

		/*
		 * If it's not free then the data will go where the
		 * leaf data starts now, if it works at all.
		 */
		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
			if (be16_to_cpu(dup->length) + (be32_to_cpu(btp->stale) - 1) *
			    (uint)sizeof(*blp) < len)
				dup = NULL;
		} else if ((be32_to_cpu(btp->stale) - 1) * (uint)sizeof(*blp) < len)
			dup = NULL;
		else
			dup = (xfs_dir2_data_unused_t *)blp;
		goto out;
	}

	/*
	 * no stale entries, so just use free space.
	 * Tag just before the first leaf entry.
	 */
	tagp = (__be16 *)blp - 1;

	/* Data object just before the first leaf entry.  */
	enddup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));

	/*
	 * If it's not free then can't do this add without cleaning up:
	 * the space before the first leaf entry needs to be free so it
	 * can be expanded to hold the pointer to the new entry.
	 */
	if (be16_to_cpu(enddup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
		/*
		 * Check out the biggest freespace and see if it's the same one.
		 */
		dup = (xfs_dir2_data_unused_t *)
		      ((char *)hdr + be16_to_cpu(bf[0].offset));
		if (dup != enddup) {
			/*
			 * Not the same free entry, just check its length.
			 */
			if (be16_to_cpu(dup->length) < len)
				dup = NULL;
			goto out;
		}

		/*
		 * It is the biggest freespace, can it hold the leaf too?
		 */
		if (be16_to_cpu(dup->length) < len + (uint)sizeof(*blp)) {
			/*
			 * Yes, use the second-largest entry instead if it works.
			 */
			if (be16_to_cpu(bf[1].length) >= len)
				dup = (xfs_dir2_data_unused_t *)
				      ((char *)hdr + be16_to_cpu(bf[1].offset));
			else
				dup = NULL;
		}
	}
out:
	*tagpp = tagp;
	*dupp = dup;
	*enddupp = enddup;
}

/*
 * compact the leaf entries.
 * Leave the highest-numbered stale entry stale.
 * XXX should be the one closest to mid but mid is not yet computed.
 */
static void
xfs_dir2_block_compact(

Annotation

Implementation Notes