fs/ntfs/aops.c

Source file repositories/reference/linux-study-clean/fs/ntfs/aops.c

File Facts

System
Linux kernel
Corpus path
fs/ntfs/aops.c
Extension
.c
Size
9595 bytes
Lines
306
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 (NInoEncrypted(ni)) {
			folio_unlock(folio);
			return -EOPNOTSUPP;
		}
		/* Compressed data streams are handled in compress.c. */
		if (NInoNonResident(ni) && NInoCompressed(ni))
			return ntfs_read_compressed_block(folio);
	}

	iomap_read_folio(&ntfs_read_iomap_ops, &ctx, NULL);
	return 0;
}

/*
 * ntfs_bmap - map logical file block to physical device block
 * @mapping:	address space mapping to which the block to be mapped belongs
 * @block:	logical block to map to its physical device block
 *
 * For regular, non-resident files (i.e. not compressed and not encrypted), map
 * the logical @block belonging to the file described by the address space
 * mapping @mapping to its physical device block.
 *
 * The size of the block is equal to the @s_blocksize field of the super block
 * of the mounted file system which is guaranteed to be smaller than or equal
 * to the cluster size thus the block is guaranteed to fit entirely inside the
 * cluster which means we do not need to care how many contiguous bytes are
 * available after the beginning of the block.
 *
 * Return the physical device block if the mapping succeeded or 0 if the block
 * is sparse or there was an error.
 *
 * Note: This is a problem if someone tries to run bmap() on $Boot system file
 * as that really is in block zero but there is nothing we can do.  bmap() is
 * just broken in that respect (just like it cannot distinguish sparse from
 * not available or error).
 */
static sector_t ntfs_bmap(struct address_space *mapping, sector_t block)
{
	s64 ofs, size;
	loff_t i_size;
	s64 lcn;
	unsigned long blocksize, flags;
	struct ntfs_inode *ni = NTFS_I(mapping->host);
	struct ntfs_volume *vol = ni->vol;
	unsigned int delta;
	unsigned char blocksize_bits;

	ntfs_debug("Entering for mft_no 0x%llx, logical block 0x%llx.",
			ni->mft_no, (unsigned long long)block);
	if (ni->type != AT_DATA || !NInoNonResident(ni) || NInoEncrypted(ni) ||
	    NInoMstProtected(ni)) {
		ntfs_error(vol->sb, "BMAP does not make sense for %s attributes, returning 0.",
				(ni->type != AT_DATA) ? "non-data" :
				(!NInoNonResident(ni) ? "resident" :
				"encrypted"));
		return 0;
	}
	/* None of these can happen. */
	blocksize = vol->sb->s_blocksize;
	blocksize_bits = vol->sb->s_blocksize_bits;
	ofs = (s64)block << blocksize_bits;
	read_lock_irqsave(&ni->size_lock, flags);
	size = ni->initialized_size;
	i_size = i_size_read(VFS_I(ni));
	read_unlock_irqrestore(&ni->size_lock, flags);
	/*
	 * If the offset is outside the initialized size or the block straddles
	 * the initialized size then pretend it is a hole unless the
	 * initialized size equals the file size.
	 */
	if (unlikely(ofs >= size || (ofs + blocksize > size && size < i_size)))
		goto hole;
	down_read(&ni->runlist.lock);
	lcn = ntfs_attr_vcn_to_lcn_nolock(ni, ntfs_bytes_to_cluster(vol, ofs),
			false);
	up_read(&ni->runlist.lock);
	if (unlikely(lcn < LCN_HOLE)) {
		/*
		 * Step down to an integer to avoid gcc doing a long long
		 * comparision in the switch when we know @lcn is between
		 * LCN_HOLE and LCN_EIO (i.e. -1 to -5).
		 *
		 * Otherwise older gcc (at least on some architectures) will
		 * try to use __cmpdi2() which is of course not available in
		 * the kernel.
		 */
		switch ((int)lcn) {
		case LCN_ENOENT:
			/*
			 * If the offset is out of bounds then pretend it is a

Annotation

Implementation Notes