Commit 26a4c0c6 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: refactor punch hole code 



Move common code in ext4_ind_punch_hole() and ext4_ext_punch_hole()
into ext4_punch_hole().  This saves over 150 lines of code.

This also fixes a potential bug when the punch_hole() code is racing
against indirect-to-extents or extents-to-indirect migation.  We are
currently using i_mutex to protect against changes to the inode flag;
specifically, the append-only, immutable, and extents inode flags.  So
we need to take i_mutex before deciding whether to use the
extents-specific or indirect-specific punch_hole code.

Also, there was a missing call to ext4_inode_block_unlocked_dio() in
the indirect punch codepath.  This was added in commit 02d262df
to block DIO readers racing against the punch operation in the
codepath for extent-mapped inodes, but it was missing for
indirect-block mapped inodes.  One of the advantages of refactoring
the code is that it makes such oversights much less likely.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 781f143e

fs/ext4/ext4.h

+4 −3
Original line number Diff line number Diff line
@@ -2110,7 +2110,8 @@ extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb, 
extern int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock);

extern int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk);

extern void ext4_ind_truncate(struct inode *inode);

extern int ext4_ind_punch_hole(struct file *file, loff_t offset, loff_t length);

extern int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,

				 ext4_lblk_t first, ext4_lblk_t stop);



/* ioctl.c */

extern long ext4_ioctl(struct file *, unsigned int, unsigned long);
@@ -2575,8 +2576,8 @@ extern int ext4_ext_index_trans_blocks(struct inode *inode, int nrblocks, 
extern int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,

			       struct ext4_map_blocks *map, int flags);

extern void ext4_ext_truncate(struct inode *);

extern int ext4_ext_punch_hole(struct file *file, loff_t offset,

				loff_t length);

extern int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,

				 ext4_lblk_t end);

extern void ext4_ext_init(struct super_block *);

extern void ext4_ext_release(struct super_block *);

extern long ext4_fallocate(struct file *file, int mode, loff_t offset,

fs/ext4/extents.c

+2 −183
Original line number Diff line number Diff line
@@ -2599,7 +2599,7 @@ ext4_ext_more_to_rm(struct ext4_ext_path *path) 
	return 1;

}



static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,

int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,

			  ext4_lblk_t end)

{

	struct super_block *sb = inode->i_sb;
@@ -4623,187 +4623,6 @@ static int ext4_xattr_fiemap(struct inode *inode, 
	return (error < 0 ? error : 0);

}



/*

 * ext4_ext_punch_hole

 *

 * Punches a hole of "length" bytes in a file starting

 * at byte "offset"

 *

 * @inode:  The inode of the file to punch a hole in

 * @offset: The starting byte offset of the hole

 * @length: The length of the hole

 *

 * Returns the number of blocks removed or negative on err

 */

int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)

{

	struct inode *inode = file_inode(file);

	struct super_block *sb = inode->i_sb;

	ext4_lblk_t first_block, stop_block;

	struct address_space *mapping = inode->i_mapping;

	handle_t *handle;

	loff_t first_page, last_page, page_len;

	loff_t first_page_offset, last_page_offset;

	int credits, err = 0;



	/*

	 * Write out all dirty pages to avoid race conditions

	 * Then release them.

	 */

	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {

		err = filemap_write_and_wait_range(mapping,

			offset, offset + length - 1);



		if (err)

			return err;

	}



	mutex_lock(&inode->i_mutex);

	/* It's not possible punch hole on append only file */

	if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {

		err = -EPERM;

		goto out_mutex;

	}

	if (IS_SWAPFILE(inode)) {

		err = -ETXTBSY;

		goto out_mutex;

	}



	/* No need to punch hole beyond i_size */

	if (offset >= inode->i_size)

		goto out_mutex;



	/*

	 * If the hole extends beyond i_size, set the hole

	 * to end after the page that contains i_size

	 */

	if (offset + length > inode->i_size) {

		length = inode->i_size +

		   PAGE_CACHE_SIZE - (inode->i_size & (PAGE_CACHE_SIZE - 1)) -

		   offset;

	}



	first_page = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	last_page = (offset + length) >> PAGE_CACHE_SHIFT;



	first_page_offset = first_page << PAGE_CACHE_SHIFT;

	last_page_offset = last_page << PAGE_CACHE_SHIFT;



	/* Now release the pages */

	if (last_page_offset > first_page_offset) {

		truncate_pagecache_range(inode, first_page_offset,

					 last_page_offset - 1);

	}



	/* Wait all existing dio workers, newcomers will block on i_mutex */

	ext4_inode_block_unlocked_dio(inode);

	err = ext4_flush_unwritten_io(inode);

	if (err)

		goto out_dio;

	inode_dio_wait(inode);



	credits = ext4_writepage_trans_blocks(inode);

	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);

	if (IS_ERR(handle)) {

		err = PTR_ERR(handle);

		goto out_dio;

	}





	/*

	 * Now we need to zero out the non-page-aligned data in the

	 * pages at the start and tail of the hole, and unmap the buffer

	 * heads for the block aligned regions of the page that were

	 * completely zeroed.

	 */

	if (first_page > last_page) {

		/*

		 * If the file space being truncated is contained within a page

		 * just zero out and unmap the middle of that page

		 */

		err = ext4_discard_partial_page_buffers(handle,

			mapping, offset, length, 0);



		if (err)

			goto out;

	} else {

		/*

		 * zero out and unmap the partial page that contains

		 * the start of the hole

		 */

		page_len  = first_page_offset - offset;

		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle, mapping,

						   offset, page_len, 0);

			if (err)

				goto out;

		}



		/*

		 * zero out and unmap the partial page that contains

		 * the end of the hole

		 */

		page_len = offset + length - last_page_offset;

		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle, mapping,

					last_page_offset, page_len, 0);

			if (err)

				goto out;

		}

	}



	/*

	 * If i_size is contained in the last page, we need to

	 * unmap and zero the partial page after i_size

	 */

	if (inode->i_size >> PAGE_CACHE_SHIFT == last_page &&

	   inode->i_size % PAGE_CACHE_SIZE != 0) {



		page_len = PAGE_CACHE_SIZE -

			(inode->i_size & (PAGE_CACHE_SIZE - 1));



		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle,

			  mapping, inode->i_size, page_len, 0);



			if (err)

				goto out;

		}

	}



	first_block = (offset + sb->s_blocksize - 1) >>

		EXT4_BLOCK_SIZE_BITS(sb);

	stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);



	/* If there are no blocks to remove, return now */

	if (first_block >= stop_block)

		goto out;



	down_write(&EXT4_I(inode)->i_data_sem);

	ext4_discard_preallocations(inode);



	err = ext4_es_remove_extent(inode, first_block,

				    stop_block - first_block);

	err = ext4_ext_remove_space(inode, first_block, stop_block - 1);



	ext4_discard_preallocations(inode);



	if (IS_SYNC(inode))

		ext4_handle_sync(handle);



	up_write(&EXT4_I(inode)->i_data_sem);



out:

	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);

	ext4_mark_inode_dirty(handle, inode);

	ext4_journal_stop(handle);

out_dio:

	ext4_inode_resume_unlocked_dio(inode);

out_mutex:

	mutex_unlock(&inode->i_mutex);

	return err;

}



int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,

		__u64 start, __u64 len)

{

fs/ext4/indirect.c

+2 −156
Original line number Diff line number Diff line
@@ -1434,7 +1434,7 @@ err: 
	return ret;

}



static int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,

int ext4_free_hole_blocks(handle_t *handle, struct inode *inode,

			  ext4_lblk_t first, ext4_lblk_t stop)

{

	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
@@ -1469,157 +1469,3 @@ err: 
	return ret;

}

int ext4_ind_punch_hole(struct file *file, loff_t offset, loff_t length)

{

	struct inode *inode = file_inode(file);

	struct super_block *sb = inode->i_sb;

	ext4_lblk_t first_block, stop_block;

	struct address_space *mapping = inode->i_mapping;

	handle_t *handle = NULL;

	loff_t first_page, last_page, page_len;

	loff_t first_page_offset, last_page_offset;

	int err = 0;



	/*

	 * Write out all dirty pages to avoid race conditions

	 * Then release them.

	 */

	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {

		err = filemap_write_and_wait_range(mapping,

			offset, offset + length - 1);

		if (err)

			return err;

	}



	mutex_lock(&inode->i_mutex);

	/* It's not possible punch hole on append only file */

	if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {

		err = -EPERM;

		goto out_mutex;

	}

	if (IS_SWAPFILE(inode)) {

		err = -ETXTBSY;

		goto out_mutex;

	}



	/* No need to punch hole beyond i_size */

	if (offset >= inode->i_size)

		goto out_mutex;



	/*

	 * If the hole extents beyond i_size, set the hole

	 * to end after the page that contains i_size

	 */

	if (offset + length > inode->i_size) {

		length = inode->i_size +

		    PAGE_CACHE_SIZE - (inode->i_size & (PAGE_CACHE_SIZE - 1)) -

		    offset;

	}



	first_page = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	last_page = (offset + length) >> PAGE_CACHE_SHIFT;



	first_page_offset = first_page << PAGE_CACHE_SHIFT;

	last_page_offset = last_page << PAGE_CACHE_SHIFT;



	/* Now release the pages */

	if (last_page_offset > first_page_offset) {

		truncate_pagecache_range(inode, first_page_offset,

					 last_page_offset - 1);

	}



	/* Wait all existing dio works, newcomers will block on i_mutex */

	inode_dio_wait(inode);



	handle = start_transaction(inode);

	if (IS_ERR(handle))

		goto out_mutex;



	/*

	 * Now we need to zero out the non-page-aligned data in the

	 * pages at the start and tail of the hole, and unmap the buffer

	 * heads for the block aligned regions of the page that were

	 * completely zerod.

	 */

	if (first_page > last_page) {

		/*

		 * If the file space being truncated is contained within a page

		 * just zero out and unmap the middle of that page

		 */

		err = ext4_discard_partial_page_buffers(handle,

			mapping, offset, length, 0);

		if (err)

			goto out;

	} else {

		/*

		 * Zero out and unmap the paritial page that contains

		 * the start of the hole

		 */

		page_len = first_page_offset - offset;

		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle, mapping,

							offset, page_len, 0);

			if (err)

				goto out;

		}



		/*

		 * Zero out and unmap the partial page that contains

		 * the end of the hole

		 */

		page_len = offset + length - last_page_offset;

		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle, mapping,

						last_page_offset, page_len, 0);

			if (err)

				goto out;

		}

	}



	/*

	 * If i_size contained in the last page, we need to

	 * unmap and zero the paritial page after i_size

	 */

	if (inode->i_size >> PAGE_CACHE_SHIFT == last_page &&

	    inode->i_size % PAGE_CACHE_SIZE != 0) {

		page_len = PAGE_CACHE_SIZE -

			(inode->i_size & (PAGE_CACHE_SIZE - 1));

		if (page_len > 0) {

			err = ext4_discard_partial_page_buffers(handle,

				mapping, inode->i_size, page_len, 0);

			if (err)

				goto out;

		}

	}



	first_block = (offset + sb->s_blocksize - 1) >>

		EXT4_BLOCK_SIZE_BITS(sb);

	stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);



	if (first_block >= stop_block)

		goto out;



	down_write(&EXT4_I(inode)->i_data_sem);

	ext4_discard_preallocations(inode);



	err = ext4_es_remove_extent(inode, first_block,

				    stop_block - first_block);

	err = ext4_free_hole_blocks(handle, inode, first_block, stop_block);



	ext4_discard_preallocations(inode);



	if (IS_SYNC(inode))

		ext4_handle_sync(handle);



	up_write(&EXT4_I(inode)->i_data_sem);



out:

	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);

	ext4_mark_inode_dirty(handle, inode);

	ext4_journal_stop(handle);



out_mutex:

	mutex_unlock(&inode->i_mutex);



	return err;

}

fs/ext4/inode.c

+175 −5
Original line number Diff line number Diff line
@@ -3566,20 +3566,190 @@ int ext4_can_truncate(struct inode *inode) 
int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)

{

	struct inode *inode = file_inode(file);

	struct super_block *sb = inode->i_sb;

	ext4_lblk_t first_block, stop_block;

	struct address_space *mapping = inode->i_mapping;

	loff_t first_page, last_page, page_len;

	loff_t first_page_offset, last_page_offset;

	handle_t *handle;

	unsigned int credits;

	int ret = 0;



	if (!S_ISREG(inode->i_mode))

		return -EOPNOTSUPP;



	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		return ext4_ind_punch_hole(file, offset, length);



	if (EXT4_SB(inode->i_sb)->s_cluster_ratio > 1) {

	if (EXT4_SB(sb)->s_cluster_ratio > 1) {

		/* TODO: Add support for bigalloc file systems */

		return -EOPNOTSUPP;

	}



	trace_ext4_punch_hole(inode, offset, length);



	return ext4_ext_punch_hole(file, offset, length);

	/*

	 * Write out all dirty pages to avoid race conditions

	 * Then release them.

	 */

	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {

		ret = filemap_write_and_wait_range(mapping, offset,

						   offset + length - 1);

		if (ret)

			return ret;

	}



	mutex_lock(&inode->i_mutex);

	/* It's not possible punch hole on append only file */

	if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {

		ret = -EPERM;

		goto out_mutex;

	}

	if (IS_SWAPFILE(inode)) {

		ret = -ETXTBSY;

		goto out_mutex;

	}



	/* No need to punch hole beyond i_size */

	if (offset >= inode->i_size)

		goto out_mutex;



	/*

	 * If the hole extends beyond i_size, set the hole

	 * to end after the page that contains i_size

	 */

	if (offset + length > inode->i_size) {

		length = inode->i_size +

		   PAGE_CACHE_SIZE - (inode->i_size & (PAGE_CACHE_SIZE - 1)) -

		   offset;

	}



	first_page = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	last_page = (offset + length) >> PAGE_CACHE_SHIFT;



	first_page_offset = first_page << PAGE_CACHE_SHIFT;

	last_page_offset = last_page << PAGE_CACHE_SHIFT;



	/* Now release the pages */

	if (last_page_offset > first_page_offset) {

		truncate_pagecache_range(inode, first_page_offset,

					 last_page_offset - 1);

	}



	/* Wait all existing dio workers, newcomers will block on i_mutex */

	ext4_inode_block_unlocked_dio(inode);

	ret = ext4_flush_unwritten_io(inode);

	if (ret)

		goto out_dio;

	inode_dio_wait(inode);



	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		credits = ext4_writepage_trans_blocks(inode);

	else

		credits = ext4_blocks_for_truncate(inode);

	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);

	if (IS_ERR(handle)) {

		ret = PTR_ERR(handle);

		ext4_std_error(sb, ret);

		goto out_dio;

	}



	/*

	 * Now we need to zero out the non-page-aligned data in the

	 * pages at the start and tail of the hole, and unmap the

	 * buffer heads for the block aligned regions of the page that

	 * were completely zeroed.

	 */

	if (first_page > last_page) {

		/*

		 * If the file space being truncated is contained

		 * within a page just zero out and unmap the middle of

		 * that page

		 */

		ret = ext4_discard_partial_page_buffers(handle,

			mapping, offset, length, 0);



		if (ret)

			goto out_stop;

	} else {

		/*

		 * zero out and unmap the partial page that contains

		 * the start of the hole

		 */

		page_len = first_page_offset - offset;

		if (page_len > 0) {

			ret = ext4_discard_partial_page_buffers(handle, mapping,

						offset, page_len, 0);

			if (ret)

				goto out_stop;

		}



		/*

		 * zero out and unmap the partial page that contains

		 * the end of the hole

		 */

		page_len = offset + length - last_page_offset;

		if (page_len > 0) {

			ret = ext4_discard_partial_page_buffers(handle, mapping,

					last_page_offset, page_len, 0);

			if (ret)

				goto out_stop;

		}

	}



	/*

	 * If i_size is contained in the last page, we need to

	 * unmap and zero the partial page after i_size

	 */

	if (inode->i_size >> PAGE_CACHE_SHIFT == last_page &&

	   inode->i_size % PAGE_CACHE_SIZE != 0) {

		page_len = PAGE_CACHE_SIZE -

			(inode->i_size & (PAGE_CACHE_SIZE - 1));



		if (page_len > 0) {

			ret = ext4_discard_partial_page_buffers(handle,

					mapping, inode->i_size, page_len, 0);



			if (ret)

				goto out_stop;

		}

	}



	first_block = (offset + sb->s_blocksize - 1) >>

		EXT4_BLOCK_SIZE_BITS(sb);

	stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);



	/* If there are no blocks to remove, return now */

	if (first_block >= stop_block)

		goto out_stop;



	down_write(&EXT4_I(inode)->i_data_sem);

	ext4_discard_preallocations(inode);



	ret = ext4_es_remove_extent(inode, first_block,

				    stop_block - first_block);

	if (ret) {

		up_write(&EXT4_I(inode)->i_data_sem);

		goto out_stop;

	}



	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		ret = ext4_ext_remove_space(inode, first_block,

					    stop_block - 1);

	else

		ret = ext4_free_hole_blocks(handle, inode, first_block,

					    stop_block);



	ext4_discard_preallocations(inode);

	if (IS_SYNC(inode))

		ext4_handle_sync(handle);

	up_write(&EXT4_I(inode)->i_data_sem);

	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);

	ext4_mark_inode_dirty(handle, inode);

out_stop:

	ext4_journal_stop(handle);

out_dio:

	ext4_inode_resume_unlocked_dio(inode);

out_mutex:

	mutex_unlock(&inode->i_mutex);

	return ret;

}



/*

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