fs/fat/file.c

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

File Facts

System
Linux kernel
Corpus path
fs/fat/file.c
Extension
.c
Size
16181 bytes
Lines
616
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: operation-table or driver-model contract
Status
pattern 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

const struct file_operations fat_file_operations = {
	.llseek		= generic_file_llseek,
	.read_iter	= generic_file_read_iter,
	.write_iter	= generic_file_write_iter,
	.mmap_prepare	= generic_file_mmap_prepare,
	.release	= fat_file_release,
	.unlocked_ioctl	= fat_generic_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
	.fsync		= fat_file_fsync,
	.splice_read	= filemap_splice_read,
	.splice_write	= iter_file_splice_write,
	.fallocate	= fat_fallocate,
	.setlease	= generic_setlease,
};

static int fat_cont_expand(struct inode *inode, loff_t size)
{
	struct address_space *mapping = inode->i_mapping;
	loff_t start = inode->i_size, count = size - inode->i_size;
	int err;

	err = generic_cont_expand_simple(inode, size);
	if (err)
		goto out;

	fat_truncate_time(inode, NULL, FAT_UPDATE_CMTIME);
	mark_inode_dirty(inode);
	if (IS_SYNC(inode)) {
		int err2;

		/*
		 * Opencode syncing since we don't have a file open to use
		 * standard fsync path.
		 */
		err = filemap_fdatawrite_range(mapping, start,
					       start + count - 1);
		err2 = mmb_sync(&MSDOS_I(inode)->i_metadata_bhs);
		if (!err)
			err = err2;
		err2 = write_inode_now(inode, 1);
		if (!err)
			err = err2;
		if (!err) {
			err =  filemap_fdatawait_range(mapping, start,
						       start + count - 1);
		}
	}
out:
	return err;
}

/*
 * Preallocate space for a file. This implements fat's fallocate file
 * operation, which gets called from sys_fallocate system call. User
 * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
 * we just allocate clusters without zeroing them out. Otherwise we
 * allocate and zero out clusters via an expanding truncate.
 */
static long fat_fallocate(struct file *file, int mode,
			  loff_t offset, loff_t len)
{
	int nr_cluster; /* Number of clusters to be allocated */
	loff_t mm_bytes; /* Number of bytes to be allocated for file */
	loff_t ondisksize; /* block aligned on-disk size in bytes*/
	struct inode *inode = file->f_mapping->host;
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int err = 0;

	/* No support for hole punch or other fallocate flags. */
	if (mode & ~FALLOC_FL_KEEP_SIZE)
		return -EOPNOTSUPP;

	/* No support for dir */
	if (!S_ISREG(inode->i_mode))
		return -EOPNOTSUPP;

	inode_lock(inode);
	if (mode & FALLOC_FL_KEEP_SIZE) {
		ondisksize = inode->i_blocks << 9;
		if ((offset + len) <= ondisksize)
			goto error;

		/* First compute the number of clusters to be allocated */
		mm_bytes = offset + len - ondisksize;
		nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
			sbi->cluster_bits;

		/* Start the allocation.We are not zeroing out the clusters */
		while (nr_cluster-- > 0) {

Annotation

Implementation Notes