fs/ext4/file.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  *  linux/fs/ext4/file.c
  *
  * Copyright (C) 1992, 1993, 1994, 1995
  * Remy Card (card@masi.ibp.fr)
  * Laboratoire MASI - Institut Blaise Pascal
  * Universite Pierre et Marie Curie (Paris VI)
  *
  *  from
  *
  *  linux/fs/minix/file.c
  *
  *  Copyright (C) 1991, 1992  Linus Torvalds
  *
  *  ext4 fs regular file handling primitives
  *
  *  64-bit file support on 64-bit platforms by Jakub Jelinek
  *	(jj@sunsite.ms.mff.cuni.cz)
  */

 #include <linux/time.h>
 #include <linux/fs.h>
 #include <linux/jbd2.h>
 #include <linux/mount.h>
 #include <linux/path.h>
 #include <linux/aio.h>
 #include <linux/quotaops.h>
 #include <linux/pagevec.h>
 #include "ext4.h"
 #include "ext4_jbd2.h"
 #include "xattr.h"
 #include "acl.h"

 /*
  * Called when an inode is released. Note that this is different
  * from ext4_file_open: open gets called at every open, but release
  * gets called only when /all/ the files are closed.
  */
 static int ext4_release_file(struct inode *inode, struct file *filp)
 {
 	if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
 		ext4_alloc_da_blocks(inode);
 		ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
 	}
 	/* if we are the last writer on the inode, drop the block reservation */
 	if ((filp->f_mode & FMODE_WRITE) &&
 			(atomic_read(&inode->i_writecount) == 1) &&
 		        !EXT4_I(inode)->i_reserved_data_blocks)
 	{
 		down_write(&EXT4_I(inode)->i_data_sem);
 		ext4_discard_preallocations(inode);
 		up_write(&EXT4_I(inode)->i_data_sem);
 	}
 	if (is_dx(inode) && filp->private_data)
 		ext4_htree_free_dir_info(filp->private_data);

 	return 0;
 }

 void ext4_unwritten_wait(struct inode *inode)
 {
 	wait_queue_head_t *wq = ext4_ioend_wq(inode);

 	wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
 }

 /*
  * This tests whether the IO in question is block-aligned or not.
  * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
  * are converted to written only after the IO is complete.  Until they are
  * mapped, these blocks appear as holes, so dio_zero_block() will assume that
  * it needs to zero out portions of the start and/or end block.  If 2 AIO
  * threads are at work on the same unwritten block, they must be synchronized
  * or one thread will zero the other's data, causing corruption.
  */
 static int
 ext4_unaligned_aio(struct inode *inode, const struct iovec *iov,
 		   unsigned long nr_segs, loff_t pos)
 {
 	struct super_block *sb = inode->i_sb;
 	int blockmask = sb->s_blocksize - 1;
 	size_t count = iov_length(iov, nr_segs);
 	loff_t final_size = pos + count;

 	if (pos >= inode->i_size)
 		return 0;

 	if ((pos & blockmask) || (final_size & blockmask))
 		return 1;

 	return 0;
 }

 static ssize_t
 ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov,
 		    unsigned long nr_segs, loff_t pos)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
 	struct blk_plug plug;
 	int unaligned_aio = 0;
 	ssize_t ret;
 	int overwrite = 0;
 	size_t length = iov_length(iov, nr_segs);

 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
 	    !is_sync_kiocb(iocb))
 		unaligned_aio = ext4_unaligned_aio(inode, iov, nr_segs, pos);

 	/* Unaligned direct AIO must be serialized; see comment above */
 	if (unaligned_aio) {
 		mutex_lock(ext4_aio_mutex(inode));
 		ext4_unwritten_wait(inode);
 	}

 	BUG_ON(iocb->ki_pos != pos);

 	mutex_lock(&inode->i_mutex);
 	blk_start_plug(&plug);

 	iocb->private = &overwrite;

 	/* check whether we do a DIO overwrite or not */
 	if (ext4_should_dioread_nolock(inode) && !unaligned_aio &&
 	    !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
 		struct ext4_map_blocks map;
 		unsigned int blkbits = inode->i_blkbits;
 		int err, len;

 		map.m_lblk = pos >> blkbits;
 		map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
 			- map.m_lblk;
 		len = map.m_len;

 		err = ext4_map_blocks(NULL, inode, &map, 0);
 		/*
 		 * 'err==len' means that all of blocks has been preallocated no
 		 * matter they are initialized or not.  For excluding
 		 * uninitialized extents, we need to check m_flags.  There are
 		 * two conditions that indicate for initialized extents.
 		 * 1) If we hit extent cache, EXT4_MAP_MAPPED flag is returned;
 		 * 2) If we do a real lookup, non-flags are returned.
 		 * So we should check these two conditions.
 		 */
 		if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
 			overwrite = 1;
 	}

 	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
 	mutex_unlock(&inode->i_mutex);

 	if (ret > 0) {
 		ssize_t err;

 		err = generic_write_sync(file, iocb->ki_pos - ret, ret);
 		if (err < 0)
 			ret = err;
 	}
 	blk_finish_plug(&plug);

 	if (unaligned_aio)
 		mutex_unlock(ext4_aio_mutex(inode));

 	return ret;
 }

 static ssize_t
 ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 		unsigned long nr_segs, loff_t pos)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t ret;

 	/*
 	 * If we have encountered a bitmap-format file, the size limit
 	 * is smaller than s_maxbytes, which is for extent-mapped files.
 	 */

 	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
 		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 		size_t length = iov_length(iov, nr_segs);

 		if ((pos > sbi->s_bitmap_maxbytes ||
 		    (pos == sbi->s_bitmap_maxbytes && length > 0)))
 			return -EFBIG;

 		if (pos + length > sbi->s_bitmap_maxbytes) {
 			nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
 					      sbi->s_bitmap_maxbytes - pos);
 		}
 	}

 	if (unlikely(iocb->ki_filp->f_flags & O_DIRECT))
 		ret = ext4_file_dio_write(iocb, iov, nr_segs, pos);
 	else
 		ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

 	return ret;
 }

 static const struct vm_operations_struct ext4_file_vm_ops = {
 	.fault		= filemap_fault,
 	.page_mkwrite   = ext4_page_mkwrite,
 	.remap_pages	= generic_file_remap_pages,
 };

 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct address_space *mapping = file->f_mapping;

 	if (!mapping->a_ops->readpage)
 		return -ENOEXEC;
 	file_accessed(file);
 	vma->vm_ops = &ext4_file_vm_ops;
 	return 0;
 }

 static int ext4_file_open(struct inode * inode, struct file * filp)
 {
 	struct super_block *sb = inode->i_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct vfsmount *mnt = filp->f_path.mnt;
 	struct path path;
 	char buf[64], *cp;

 	if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
 		     !(sb->s_flags & MS_RDONLY))) {
 		sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
 		/*
 		 * Sample where the filesystem has been mounted and
 		 * store it in the superblock for sysadmin convenience
 		 * when trying to sort through large numbers of block
 		 * devices or filesystem images.
 		 */
 		memset(buf, 0, sizeof(buf));
 		path.mnt = mnt;
 		path.dentry = mnt->mnt_root;
 		cp = d_path(&path, buf, sizeof(buf));
 		if (!IS_ERR(cp)) {
 			handle_t *handle;
 			int err;

 			handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
 			if (IS_ERR(handle))
 				return PTR_ERR(handle);
 			err = ext4_journal_get_write_access(handle, sbi->s_sbh);
 			if (err) {
 				ext4_journal_stop(handle);
 				return err;
 			}
 			strlcpy(sbi->s_es->s_last_mounted, cp,
 				sizeof(sbi->s_es->s_last_mounted));
 			ext4_handle_dirty_super(handle, sb);
 			ext4_journal_stop(handle);
 		}
 	}
 	/*
 	 * Set up the jbd2_inode if we are opening the inode for
 	 * writing and the journal is present
 	 */
 	if (filp->f_mode & FMODE_WRITE) {
 		int ret = ext4_inode_attach_jinode(inode);
 		if (ret < 0)
 			return ret;
 	}
 	return dquot_file_open(inode, filp);
 }

 /*
  * Here we use ext4_map_blocks() to get a block mapping for a extent-based
  * file rather than ext4_ext_walk_space() because we can introduce
  * SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
  * function.  When extent status tree has been fully implemented, it will
  * track all extent status for a file and we can directly use it to
  * retrieve the offset for SEEK_DATA/SEEK_HOLE.
  */

 /*
  * When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
  * lookup page cache to check whether or not there has some data between
  * [startoff, endoff] because, if this range contains an unwritten extent,
  * we determine this extent as a data or a hole according to whether the
  * page cache has data or not.
  */
 static int ext4_find_unwritten_pgoff(struct inode *inode,
 				     int whence,
 				     struct ext4_map_blocks *map,
 				     loff_t *offset)
 {
 	struct pagevec pvec;
 	unsigned int blkbits;
 	pgoff_t index;
 	pgoff_t end;
 	loff_t endoff;
 	loff_t startoff;
 	loff_t lastoff;
 	int found = 0;

 	blkbits = inode->i_sb->s_blocksize_bits;
 	startoff = *offset;
 	lastoff = startoff;
 	endoff = (loff_t)(map->m_lblk + map->m_len) << blkbits;

 	index = startoff >> PAGE_CACHE_SHIFT;
 	end = endoff >> PAGE_CACHE_SHIFT;

 	pagevec_init(&pvec, 0);
 	do {
 		int i, num;
 		unsigned long nr_pages;

 		num = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
 		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
 					  (pgoff_t)num);
 		if (nr_pages == 0) {
 			if (whence == SEEK_DATA)
 				break;

 			BUG_ON(whence != SEEK_HOLE);
 			/*
 			 * If this is the first time to go into the loop and
 			 * offset is not beyond the end offset, it will be a
 			 * hole at this offset
 			 */
 			if (lastoff == startoff || lastoff < endoff)
 				found = 1;
 			break;
 		}

 		/*
 		 * If this is the first time to go into the loop and
 		 * offset is smaller than the first page offset, it will be a
 		 * hole at this offset.
 		 */
 		if (lastoff == startoff && whence == SEEK_HOLE &&
 		    lastoff < page_offset(pvec.pages[0])) {
 			found = 1;
 			break;
 		}

 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
 			struct buffer_head *bh, *head;

 			/*
 			 * If the current offset is not beyond the end of given
 			 * range, it will be a hole.
 			 */
 			if (lastoff < endoff && whence == SEEK_HOLE &&
 			    page->index > end) {
 				found = 1;
 				*offset = lastoff;
 				goto out;
 			}

 			lock_page(page);

 			if (unlikely(page->mapping != inode->i_mapping)) {
 				unlock_page(page);
 				continue;
 			}

 			if (!page_has_buffers(page)) {
 				unlock_page(page);
 				continue;
 			}

 			if (page_has_buffers(page)) {
 				lastoff = page_offset(page);
 				bh = head = page_buffers(page);
 				do {
 					if (buffer_uptodate(bh) ||
 					    buffer_unwritten(bh)) {
 						if (whence == SEEK_DATA)
 							found = 1;
 					} else {
 						if (whence == SEEK_HOLE)
 							found = 1;
 					}
 					if (found) {
 						*offset = max_t(loff_t,
 							startoff, lastoff);
 						unlock_page(page);
 						goto out;
 					}
 					lastoff += bh->b_size;
 					bh = bh->b_this_page;
 				} while (bh != head);
 			}

 			lastoff = page_offset(page) + PAGE_SIZE;
 			unlock_page(page);
 		}

 		/*
 		 * The no. of pages is less than our desired, that would be a
 		 * hole in there.
 		 */
 		if (nr_pages < num && whence == SEEK_HOLE) {
 			found = 1;
 			*offset = lastoff;
 			break;
 		}

 		index = pvec.pages[i - 1]->index + 1;
 		pagevec_release(&pvec);
 	} while (index <= end);

 out:
 	pagevec_release(&pvec);
 	return found;
 }

 /*
  * ext4_seek_data() retrieves the offset for SEEK_DATA.
  */
 static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
 {
 	struct inode *inode = file->f_mapping->host;
 	struct ext4_map_blocks map;
 	struct extent_status es;
 	ext4_lblk_t start, last, end;
 	loff_t dataoff, isize;
 	int blkbits;
 	int ret = 0;

 	mutex_lock(&inode->i_mutex);

 	isize = i_size_read(inode);
 	if (offset >= isize) {
 		mutex_unlock(&inode->i_mutex);
 		return -ENXIO;
 	}

 	blkbits = inode->i_sb->s_blocksize_bits;
 	start = offset >> blkbits;
 	last = start;
 	end = isize >> blkbits;
 	dataoff = offset;

 	do {
 		map.m_lblk = last;
 		map.m_len = end - last + 1;
 		ret = ext4_map_blocks(NULL, inode, &map, 0);
 		if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
 			if (last != start)
 				dataoff = (loff_t)last << blkbits;
 			break;
 		}

 		/*
 		 * If there is a delay extent at this offset,
 		 * it will be as a data.
 		 */
 		ext4_es_find_delayed_extent_range(inode, last, last, &es);
 		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
 			if (last != start)
 				dataoff = (loff_t)last << blkbits;
 			break;
 		}

 		/*
 		 * If there is a unwritten extent at this offset,
 		 * it will be as a data or a hole according to page
 		 * cache that has data or not.
 		 */
 		if (map.m_flags & EXT4_MAP_UNWRITTEN) {
 			int unwritten;
 			unwritten = ext4_find_unwritten_pgoff(inode, SEEK_DATA,
 							      &map, &dataoff);
 			if (unwritten)
 				break;
 		}

 		last++;
 		dataoff = (loff_t)last << blkbits;
 	} while (last <= end);

 	mutex_unlock(&inode->i_mutex);

 	if (dataoff > isize)
 		return -ENXIO;

 	return vfs_setpos(file, dataoff, maxsize);
 }

 /*
  * ext4_seek_hole() retrieves the offset for SEEK_HOLE.
  */
 static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
 {
 	struct inode *inode = file->f_mapping->host;
 	struct ext4_map_blocks map;
 	struct extent_status es;
 	ext4_lblk_t start, last, end;
 	loff_t holeoff, isize;
 	int blkbits;
 	int ret = 0;

 	mutex_lock(&inode->i_mutex);

 	isize = i_size_read(inode);
 	if (offset >= isize) {
 		mutex_unlock(&inode->i_mutex);
 		return -ENXIO;
 	}

 	blkbits = inode->i_sb->s_blocksize_bits;
 	start = offset >> blkbits;
 	last = start;
 	end = isize >> blkbits;
 	holeoff = offset;

 	do {
 		map.m_lblk = last;
 		map.m_len = end - last + 1;
 		ret = ext4_map_blocks(NULL, inode, &map, 0);
 		if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
 			last += ret;
 			holeoff = (loff_t)last << blkbits;
 			continue;
 		}

 		/*
 		 * If there is a delay extent at this offset,
 		 * we will skip this extent.
 		 */
 		ext4_es_find_delayed_extent_range(inode, last, last, &es);
 		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
 			last = es.es_lblk + es.es_len;
 			holeoff = (loff_t)last << blkbits;
 			continue;
 		}

 		/*
 		 * If there is a unwritten extent at this offset,
 		 * it will be as a data or a hole according to page
 		 * cache that has data or not.
 		 */
 		if (map.m_flags & EXT4_MAP_UNWRITTEN) {
 			int unwritten;
 			unwritten = ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
 							      &map, &holeoff);
 			if (!unwritten) {
 				last += ret;
 				holeoff = (loff_t)last << blkbits;
 				continue;
 			}
 		}

 		/* find a hole */
 		break;
 	} while (last <= end);

 	mutex_unlock(&inode->i_mutex);

 	if (holeoff > isize)
 		holeoff = isize;

 	return vfs_setpos(file, holeoff, maxsize);
 }

 /*
  * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
  * by calling generic_file_llseek_size() with the appropriate maxbytes
  * value for each.
  */
 loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct inode *inode = file->f_mapping->host;
 	loff_t maxbytes;

 	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
 		maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
 	else
 		maxbytes = inode->i_sb->s_maxbytes;

 	switch (whence) {
 	case SEEK_SET:
 	case SEEK_CUR:
 	case SEEK_END:
 		return generic_file_llseek_size(file, offset, whence,
 						maxbytes, i_size_read(inode));
 	case SEEK_DATA:
 		return ext4_seek_data(file, offset, maxbytes);
 	case SEEK_HOLE:
 		return ext4_seek_hole(file, offset, maxbytes);
 	}

 	return -EINVAL;
 }

 const struct file_operations ext4_file_operations = {
 	.llseek		= ext4_llseek,
 	.read		= do_sync_read,
 	.write		= do_sync_write,
 	.aio_read	= generic_file_aio_read,
 	.aio_write	= ext4_file_write,
 	.unlocked_ioctl = ext4_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= ext4_compat_ioctl,
 #endif
 	.mmap		= ext4_file_mmap,
 	.open		= ext4_file_open,
 	.release	= ext4_release_file,
 	.fsync		= ext4_sync_file,
 	.splice_read	= generic_file_splice_read,
 	.splice_write	= generic_file_splice_write,
 	.fallocate	= ext4_fallocate,
 };

 const struct inode_operations ext4_file_inode_operations = {
 	.setattr	= ext4_setattr,
 	.getattr	= ext4_getattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,
 	.listxattr	= ext4_listxattr,
 	.removexattr	= generic_removexattr,
 	.get_acl	= ext4_get_acl,
 	.set_acl	= ext4_set_acl,
 	.fiemap		= ext4_fiemap,
 };
	/*
	* linux/fs/ext4/file.c
	*
	* Copyright (C) 1992, 1993, 1994, 1995
	* Remy Card (card@masi.ibp.fr)
	* Laboratoire MASI - Institut Blaise Pascal
	* Universite Pierre et Marie Curie (Paris VI)
	*
	* from
	*
	* linux/fs/minix/file.c
	*
	* Copyright (C) 1991, 1992 Linus Torvalds
	*
	* ext4 fs regular file handling primitives
	*
	* 64-bit file support on 64-bit platforms by Jakub Jelinek
	* (jj@sunsite.ms.mff.cuni.cz)
	*/

	#include <linux/time.h>
	#include <linux/fs.h>
	#include <linux/jbd2.h>
	#include <linux/mount.h>
	#include <linux/path.h>
	#include <linux/aio.h>
	#include <linux/quotaops.h>
	#include <linux/pagevec.h>
	#include "ext4.h"
	#include "ext4_jbd2.h"
	#include "xattr.h"
	#include "acl.h"

	/*
	* Called when an inode is released. Note that this is different
	* from ext4_file_open: open gets called at every open, but release
	* gets called only when /all/ the files are closed.
	*/
	static int ext4_release_file(struct inode inode, struct file filp)
	{
	if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
	ext4_alloc_da_blocks(inode);
	ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
	}
	/* if we are the last writer on the inode, drop the block reservation */
	if ((filp->f_mode & FMODE_WRITE) &&
	(atomic_read(&inode->i_writecount) == 1) &&
	!EXT4_I(inode)->i_reserved_data_blocks)
	{
	down_write(&EXT4_I(inode)->i_data_sem);
	ext4_discard_preallocations(inode);
	up_write(&EXT4_I(inode)->i_data_sem);
	}
	if (is_dx(inode) && filp->private_data)
	ext4_htree_free_dir_info(filp->private_data);

	return 0;
	}

	void ext4_unwritten_wait(struct inode *inode)
	{
	wait_queue_head_t *wq = ext4_ioend_wq(inode);

	wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
	}

	/*
	* This tests whether the IO in question is block-aligned or not.
	* Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
	* are converted to written only after the IO is complete. Until they are
	* mapped, these blocks appear as holes, so dio_zero_block() will assume that
	* it needs to zero out portions of the start and/or end block. If 2 AIO
	* threads are at work on the same unwritten block, they must be synchronized
	* or one thread will zero the other's data, causing corruption.
	*/
	static int
	ext4_unaligned_aio(struct inode inode, const struct iovec iov,
	unsigned long nr_segs, loff_t pos)
	{
	struct super_block *sb = inode->i_sb;
	int blockmask = sb->s_blocksize - 1;
	size_t count = iov_length(iov, nr_segs);
	loff_t final_size = pos + count;

	if (pos >= inode->i_size)
	return 0;

	if ((pos & blockmask) \|\| (final_size & blockmask))
	return 1;

	return 0;
	}

	static ssize_t
	ext4_file_dio_write(struct kiocb iocb, const struct iovec iov,
	unsigned long nr_segs, loff_t pos)
	{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_mapping->host;
	struct blk_plug plug;
	int unaligned_aio = 0;
	ssize_t ret;
	int overwrite = 0;
	size_t length = iov_length(iov, nr_segs);

	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
	!is_sync_kiocb(iocb))
	unaligned_aio = ext4_unaligned_aio(inode, iov, nr_segs, pos);

	/* Unaligned direct AIO must be serialized; see comment above */
	if (unaligned_aio) {
	mutex_lock(ext4_aio_mutex(inode));
	ext4_unwritten_wait(inode);
	}

	BUG_ON(iocb->ki_pos != pos);

	mutex_lock(&inode->i_mutex);
	blk_start_plug(&plug);

	iocb->private = &overwrite;

	/* check whether we do a DIO overwrite or not */
	if (ext4_should_dioread_nolock(inode) && !unaligned_aio &&
	!file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
	struct ext4_map_blocks map;
	unsigned int blkbits = inode->i_blkbits;
	int err, len;

	map.m_lblk = pos >> blkbits;
	map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
	- map.m_lblk;
	len = map.m_len;

	err = ext4_map_blocks(NULL, inode, &map, 0);
	/*
	* 'err==len' means that all of blocks has been preallocated no
	* matter they are initialized or not. For excluding
	* uninitialized extents, we need to check m_flags. There are
	* two conditions that indicate for initialized extents.
	* 1) If we hit extent cache, EXT4_MAP_MAPPED flag is returned;
	* 2) If we do a real lookup, non-flags are returned.
	* So we should check these two conditions.
	*/
	if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
	overwrite = 1;
	}

	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
	mutex_unlock(&inode->i_mutex);

	if (ret > 0) {
	ssize_t err;

	err = generic_write_sync(file, iocb->ki_pos - ret, ret);
	if (err < 0)
	ret = err;
	}
	blk_finish_plug(&plug);

	if (unaligned_aio)
	mutex_unlock(ext4_aio_mutex(inode));

	return ret;
	}

	static ssize_t
	ext4_file_write(struct kiocb iocb, const struct iovec iov,
	unsigned long nr_segs, loff_t pos)
	{
	struct inode *inode = file_inode(iocb->ki_filp);
	ssize_t ret;

	/*
	* If we have encountered a bitmap-format file, the size limit
	* is smaller than s_maxbytes, which is for extent-mapped files.
	*/

	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	size_t length = iov_length(iov, nr_segs);

	if ((pos > sbi->s_bitmap_maxbytes \|\|
	(pos == sbi->s_bitmap_maxbytes && length > 0)))
	return -EFBIG;

	if (pos + length > sbi->s_bitmap_maxbytes) {
	nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
	sbi->s_bitmap_maxbytes - pos);
	}
	}

	if (unlikely(iocb->ki_filp->f_flags & O_DIRECT))
	ret = ext4_file_dio_write(iocb, iov, nr_segs, pos);
	else
	ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

	return ret;
	}

	static const struct vm_operations_struct ext4_file_vm_ops = {
	.fault = filemap_fault,
	.page_mkwrite = ext4_page_mkwrite,
	.remap_pages = generic_file_remap_pages,
	};

	static int ext4_file_mmap(struct file file, struct vm_area_struct vma)
	{
	struct address_space *mapping = file->f_mapping;

	if (!mapping->a_ops->readpage)
	return -ENOEXEC;
	file_accessed(file);
	vma->vm_ops = &ext4_file_vm_ops;
	return 0;
	}

	static int ext4_file_open(struct inode * inode, struct file * filp)
	{
	struct super_block *sb = inode->i_sb;
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct vfsmount *mnt = filp->f_path.mnt;
	struct path path;
	char buf[64], *cp;

	if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
	!(sb->s_flags & MS_RDONLY))) {
	sbi->s_mount_flags \|= EXT4_MF_MNTDIR_SAMPLED;
	/*
	* Sample where the filesystem has been mounted and
	* store it in the superblock for sysadmin convenience
	* when trying to sort through large numbers of block
	* devices or filesystem images.
	*/
	memset(buf, 0, sizeof(buf));
	path.mnt = mnt;
	path.dentry = mnt->mnt_root;
	cp = d_path(&path, buf, sizeof(buf));
	if (!IS_ERR(cp)) {
	handle_t *handle;
	int err;

	handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
	if (IS_ERR(handle))
	return PTR_ERR(handle);
	err = ext4_journal_get_write_access(handle, sbi->s_sbh);
	if (err) {
	ext4_journal_stop(handle);
	return err;
	}
	strlcpy(sbi->s_es->s_last_mounted, cp,
	sizeof(sbi->s_es->s_last_mounted));
	ext4_handle_dirty_super(handle, sb);
	ext4_journal_stop(handle);
	}
	}
	/*
	* Set up the jbd2_inode if we are opening the inode for
	* writing and the journal is present
	*/
	if (filp->f_mode & FMODE_WRITE) {
	int ret = ext4_inode_attach_jinode(inode);
	if (ret < 0)
	return ret;
	}
	return dquot_file_open(inode, filp);
	}

	/*
	* Here we use ext4_map_blocks() to get a block mapping for a extent-based
	* file rather than ext4_ext_walk_space() because we can introduce
	* SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
	* function. When extent status tree has been fully implemented, it will
	* track all extent status for a file and we can directly use it to
	* retrieve the offset for SEEK_DATA/SEEK_HOLE.
	*/

	/*
	* When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
	* lookup page cache to check whether or not there has some data between
	* [startoff, endoff] because, if this range contains an unwritten extent,
	* we determine this extent as a data or a hole according to whether the
	* page cache has data or not.
	*/
	static int ext4_find_unwritten_pgoff(struct inode *inode,
	int whence,
	struct ext4_map_blocks *map,
	loff_t *offset)
	{
	struct pagevec pvec;
	unsigned int blkbits;
	pgoff_t index;
	pgoff_t end;
	loff_t endoff;
	loff_t startoff;
	loff_t lastoff;
	int found = 0;

	blkbits = inode->i_sb->s_blocksize_bits;
	startoff = *offset;
	lastoff = startoff;
	endoff = (loff_t)(map->m_lblk + map->m_len) << blkbits;

	index = startoff >> PAGE_CACHE_SHIFT;
	end = endoff >> PAGE_CACHE_SHIFT;

	pagevec_init(&pvec, 0);
	do {
	int i, num;
	unsigned long nr_pages;

	num = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
	nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
	(pgoff_t)num);
	if (nr_pages == 0) {
	if (whence == SEEK_DATA)
	break;

	BUG_ON(whence != SEEK_HOLE);
	/*
	* If this is the first time to go into the loop and
	* offset is not beyond the end offset, it will be a
	* hole at this offset
	*/
	if (lastoff == startoff \|\| lastoff < endoff)
	found = 1;
	break;
	}

	/*
	* If this is the first time to go into the loop and
	* offset is smaller than the first page offset, it will be a
	* hole at this offset.
	*/
	if (lastoff == startoff && whence == SEEK_HOLE &&
	lastoff < page_offset(pvec.pages[0])) {
	found = 1;
	break;
	}

	for (i = 0; i < nr_pages; i++) {
	struct page *page = pvec.pages[i];
	struct buffer_head bh, head;

	/*
	* If the current offset is not beyond the end of given
	* range, it will be a hole.
	*/
	if (lastoff < endoff && whence == SEEK_HOLE &&
	page->index > end) {
	found = 1;
	*offset = lastoff;
	goto out;
	}

	lock_page(page);

	if (unlikely(page->mapping != inode->i_mapping)) {
	unlock_page(page);
	continue;
	}

	if (!page_has_buffers(page)) {
	unlock_page(page);
	continue;
	}

	if (page_has_buffers(page)) {
	lastoff = page_offset(page);
	bh = head = page_buffers(page);
	do {
	if (buffer_uptodate(bh) \|\|
	buffer_unwritten(bh)) {
	if (whence == SEEK_DATA)
	found = 1;
	} else {
	if (whence == SEEK_HOLE)
	found = 1;
	}
	if (found) {
	*offset = max_t(loff_t,
	startoff, lastoff);
	unlock_page(page);
	goto out;
	}
	lastoff += bh->b_size;
	bh = bh->b_this_page;
	} while (bh != head);
	}

	lastoff = page_offset(page) + PAGE_SIZE;
	unlock_page(page);
	}

	/*
	* The no. of pages is less than our desired, that would be a
	* hole in there.
	*/
	if (nr_pages < num && whence == SEEK_HOLE) {
	found = 1;
	*offset = lastoff;
	break;
	}

	index = pvec.pages[i - 1]->index + 1;
	pagevec_release(&pvec);
	} while (index <= end);

	out:
	pagevec_release(&pvec);
	return found;
	}

	/*
	* ext4_seek_data() retrieves the offset for SEEK_DATA.
	*/
	static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
	{
	struct inode *inode = file->f_mapping->host;
	struct ext4_map_blocks map;
	struct extent_status es;
	ext4_lblk_t start, last, end;
	loff_t dataoff, isize;
	int blkbits;
	int ret = 0;

	mutex_lock(&inode->i_mutex);

	isize = i_size_read(inode);
	if (offset >= isize) {
	mutex_unlock(&inode->i_mutex);
	return -ENXIO;
	}

	blkbits = inode->i_sb->s_blocksize_bits;
	start = offset >> blkbits;
	last = start;
	end = isize >> blkbits;
	dataoff = offset;

	do {
	map.m_lblk = last;
	map.m_len = end - last + 1;
	ret = ext4_map_blocks(NULL, inode, &map, 0);
	if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
	if (last != start)
	dataoff = (loff_t)last << blkbits;
	break;
	}

	/*
	* If there is a delay extent at this offset,
	* it will be as a data.
	*/
	ext4_es_find_delayed_extent_range(inode, last, last, &es);
	if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
	if (last != start)
	dataoff = (loff_t)last << blkbits;
	break;
	}

	/*
	* If there is a unwritten extent at this offset,
	* it will be as a data or a hole according to page
	* cache that has data or not.
	*/
	if (map.m_flags & EXT4_MAP_UNWRITTEN) {
	int unwritten;
	unwritten = ext4_find_unwritten_pgoff(inode, SEEK_DATA,
	&map, &dataoff);
	if (unwritten)
	break;
	}

	last++;
	dataoff = (loff_t)last << blkbits;
	} while (last <= end);

	mutex_unlock(&inode->i_mutex);

	if (dataoff > isize)
	return -ENXIO;

	return vfs_setpos(file, dataoff, maxsize);
	}

	/*
	* ext4_seek_hole() retrieves the offset for SEEK_HOLE.
	*/
	static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
	{
	struct inode *inode = file->f_mapping->host;
	struct ext4_map_blocks map;
	struct extent_status es;
	ext4_lblk_t start, last, end;
	loff_t holeoff, isize;
	int blkbits;
	int ret = 0;

	mutex_lock(&inode->i_mutex);

	isize = i_size_read(inode);
	if (offset >= isize) {
	mutex_unlock(&inode->i_mutex);
	return -ENXIO;
	}

	blkbits = inode->i_sb->s_blocksize_bits;
	start = offset >> blkbits;
	last = start;
	end = isize >> blkbits;
	holeoff = offset;

	do {
	map.m_lblk = last;
	map.m_len = end - last + 1;
	ret = ext4_map_blocks(NULL, inode, &map, 0);
	if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
	last += ret;
	holeoff = (loff_t)last << blkbits;
	continue;
	}

	/*
	* If there is a delay extent at this offset,
	* we will skip this extent.
	*/
	ext4_es_find_delayed_extent_range(inode, last, last, &es);
	if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
	last = es.es_lblk + es.es_len;
	holeoff = (loff_t)last << blkbits;
	continue;
	}

	/*
	* If there is a unwritten extent at this offset,
	* it will be as a data or a hole according to page
	* cache that has data or not.
	*/
	if (map.m_flags & EXT4_MAP_UNWRITTEN) {
	int unwritten;
	unwritten = ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
	&map, &holeoff);
	if (!unwritten) {
	last += ret;
	holeoff = (loff_t)last << blkbits;
	continue;
	}
	}

	/* find a hole */
	break;
	} while (last <= end);

	mutex_unlock(&inode->i_mutex);

	if (holeoff > isize)
	holeoff = isize;

	return vfs_setpos(file, holeoff, maxsize);
	}

	/*
	* ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
	* by calling generic_file_llseek_size() with the appropriate maxbytes
	* value for each.
	*/
	loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
	{
	struct inode *inode = file->f_mapping->host;
	loff_t maxbytes;

	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
	maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
	else
	maxbytes = inode->i_sb->s_maxbytes;

	switch (whence) {
	case SEEK_SET:
	case SEEK_CUR:
	case SEEK_END:
	return generic_file_llseek_size(file, offset, whence,
	maxbytes, i_size_read(inode));
	case SEEK_DATA:
	return ext4_seek_data(file, offset, maxbytes);
	case SEEK_HOLE:
	return ext4_seek_hole(file, offset, maxbytes);
	}

	return -EINVAL;
	}

	const struct file_operations ext4_file_operations = {
	.llseek = ext4_llseek,
	.read = do_sync_read,
	.write = do_sync_write,
	.aio_read = generic_file_aio_read,
	.aio_write = ext4_file_write,
	.unlocked_ioctl = ext4_ioctl,
	#ifdef CONFIG_COMPAT
	.compat_ioctl = ext4_compat_ioctl,
	#endif
	.mmap = ext4_file_mmap,
	.open = ext4_file_open,
	.release = ext4_release_file,
	.fsync = ext4_sync_file,
	.splice_read = generic_file_splice_read,
	.splice_write = generic_file_splice_write,
	.fallocate = ext4_fallocate,
	};

	const struct inode_operations ext4_file_inode_operations = {
	.setattr = ext4_setattr,
	.getattr = ext4_getattr,
	.setxattr = generic_setxattr,
	.getxattr = generic_getxattr,
	.listxattr = ext4_listxattr,
	.removexattr = generic_removexattr,
	.get_acl = ext4_get_acl,
	.set_acl = ext4_set_acl,
	.fiemap = ext4_fiemap,
	};