fs/ext4/namei.c

Source file repositories/reference/linux-study-clean/fs/ext4/namei.c

File Facts

System
Linux kernel
Corpus path
fs/ext4/namei.c
Extension
.c
Size
113654 bytes
Lines
4250
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

struct dx_tail {
	u32 dt_reserved;
	__le32 dt_checksum;	/* crc32c(uuid+inum+dirblock) */
};

static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
		struct ext4_filename *fname,
		struct ext4_dir_entry_2 **res_dir);
static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
			     struct inode *dir, struct inode *inode);

/* checksumming functions */
void ext4_initialize_dirent_tail(struct buffer_head *bh,
				 unsigned int blocksize)
{
	struct ext4_dir_entry_tail *t = EXT4_DIRENT_TAIL(bh->b_data, blocksize);

	memset(t, 0, sizeof(struct ext4_dir_entry_tail));
	t->det_rec_len = ext4_rec_len_to_disk(
			sizeof(struct ext4_dir_entry_tail), blocksize);
	t->det_reserved_ft = EXT4_FT_DIR_CSUM;
}

/* Walk through a dirent block to find a checksum "dirent" at the tail */
static struct ext4_dir_entry_tail *get_dirent_tail(struct inode *inode,
						   struct buffer_head *bh)
{
	struct ext4_dir_entry_tail *t;
	int blocksize = EXT4_BLOCK_SIZE(inode->i_sb);

#ifdef PARANOID
	struct ext4_dir_entry *d, *top;

	d = (struct ext4_dir_entry *)bh->b_data;
	top = (struct ext4_dir_entry *)(bh->b_data +
		(blocksize - sizeof(struct ext4_dir_entry_tail)));
	while (d < top && ext4_rec_len_from_disk(d->rec_len, blocksize))
		d = (struct ext4_dir_entry *)(((void *)d) +
		    ext4_rec_len_from_disk(d->rec_len, blocksize));

	if (d != top)
		return NULL;

	t = (struct ext4_dir_entry_tail *)d;
#else
	t = EXT4_DIRENT_TAIL(bh->b_data, EXT4_BLOCK_SIZE(inode->i_sb));
#endif

	if (t->det_reserved_zero1 ||
	    (ext4_rec_len_from_disk(t->det_rec_len, blocksize) !=
	     sizeof(struct ext4_dir_entry_tail)) ||
	    t->det_reserved_zero2 ||
	    t->det_reserved_ft != EXT4_FT_DIR_CSUM)
		return NULL;

	return t;
}

static __le32 ext4_dirblock_csum(struct inode *inode, void *dirent, int size)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	__u32 csum;

	csum = ext4_chksum(ei->i_csum_seed, (__u8 *)dirent, size);
	return cpu_to_le32(csum);
}

#define warn_no_space_for_csum(inode)					\
	__warn_no_space_for_csum((inode), __func__, __LINE__)

static void __warn_no_space_for_csum(struct inode *inode, const char *func,
				     unsigned int line)
{
	__ext4_warning_inode(inode, func, line,
		"No space for directory leaf checksum. Please run e2fsck -D.");
}

int ext4_dirblock_csum_verify(struct inode *inode, struct buffer_head *bh)
{
	struct ext4_dir_entry_tail *t;

	if (!ext4_has_feature_metadata_csum(inode->i_sb))
		return 1;

	t = get_dirent_tail(inode, bh);
	if (!t) {
		warn_no_space_for_csum(inode);
		return 0;
	}

Annotation

Implementation Notes