Commit 4f579ae7 authored by Lukas Czerner's avatar Lukas Czerner Committed by Theodore Ts'o
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ext4: fix punch hole on files with indirect mapping 



Currently punch hole code on files with direct/indirect mapping has some
problems which may lead to a data loss. For example (from Jan Kara):

fallocate -n -p 10240000 4096

will punch the range 10240000 - 12632064 instead of the range 1024000 -
10244096.

Also the code is a bit weird and it's not using infrastructure provided
by indirect.c, but rather creating it's own way.

This patch fixes the issues as well as making the operation to run 4
times faster from my testing (punching out 60GB file). It uses similar
approach used in ext4_ind_truncate() which takes advantage of
ext4_free_branches() function.

Also rename the ext4_free_hole_blocks() to something more sensible, like
the equivalent we have for extent mapped files. Call it
ext4_ind_remove_space().

This has been tested mostly with fsx and some xfstests which are testing
punch hole but does not require unwritten extents which are not
supported with direct/indirect mapping. Not problems showed up even with
1024k block size.

CC: stable@vger.kernel.org
Signed-off-by: default avatarLukas Czerner <lczerner@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 71d4f7d0

fs/ext4/ext4.h

+2 −2
Original line number Diff line number Diff line
@@ -2143,8 +2143,8 @@ 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);

extern void ext4_ind_truncate(handle_t *, struct inode *inode);

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

				 ext4_lblk_t first, ext4_lblk_t stop);

extern int ext4_ind_remove_space(handle_t *handle, struct inode *inode,

				 ext4_lblk_t start, ext4_lblk_t end);



/* ioctl.c */

extern long ext4_ioctl(struct file *, unsigned int, unsigned long);

fs/ext4/indirect.c

+202 −79
Original line number Diff line number Diff line
@@ -1295,97 +1295,220 @@ do_indirects: 
	}

}



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

			    struct buffer_head *parent_bh, __le32 *i_data,

			    int level, ext4_lblk_t first,

			    ext4_lblk_t count, int max)

/**

 *	ext4_ind_remove_space - remove space from the range

 *	@handle: JBD handle for this transaction

 *	@inode:	inode we are dealing with

 *	@start:	First block to remove

 *	@end:	One block after the last block to remove (exclusive)

 *

 *	Free the blocks in the defined range (end is exclusive endpoint of

 *	range). This is used by ext4_punch_hole().

 */

int ext4_ind_remove_space(handle_t *handle, struct inode *inode,

			  ext4_lblk_t start, ext4_lblk_t end)

{

	struct buffer_head *bh = NULL;

	struct ext4_inode_info *ei = EXT4_I(inode);

	__le32 *i_data = ei->i_data;

	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);

	int ret = 0;

	int i, inc;

	ext4_lblk_t offset;

	__le32 blk;



	inc = 1 << ((EXT4_BLOCK_SIZE_BITS(inode->i_sb) - 2) * level);

	for (i = 0, offset = 0; i < max; i++, i_data++, offset += inc) {

		if (offset >= count + first)

			break;

		if (*i_data == 0 || (offset + inc) <= first)

			continue;

		blk = *i_data;

		if (level > 0) {

			ext4_lblk_t first2;

			ext4_lblk_t count2;

	ext4_lblk_t offsets[4], offsets2[4];

	Indirect chain[4], chain2[4];

	Indirect *partial, *partial2;

	ext4_lblk_t max_block;

	__le32 nr = 0, nr2 = 0;

	int n = 0, n2 = 0;

	unsigned blocksize = inode->i_sb->s_blocksize;



			bh = sb_bread(inode->i_sb, le32_to_cpu(blk));

			if (!bh) {

				EXT4_ERROR_INODE_BLOCK(inode, le32_to_cpu(blk),

						       "Read failure");

				return -EIO;

	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)

					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);

	if (end >= max_block)

		end = max_block;

	if ((start >= end) || (start > max_block))

		return 0;



	n = ext4_block_to_path(inode, start, offsets, NULL);

	n2 = ext4_block_to_path(inode, end, offsets2, NULL);



	BUG_ON(n > n2);



	if ((n == 1) && (n == n2)) {

		/* We're punching only within direct block range */

		ext4_free_data(handle, inode, NULL, i_data + offsets[0],

			       i_data + offsets2[0]);

		return 0;

	} else if (n2 > n) {

		/*

		 * Start and end are on a different levels so we're going to

		 * free partial block at start, and partial block at end of

		 * the range. If there are some levels in between then

		 * do_indirects label will take care of that.

		 */



		if (n == 1) {

			/*

			 * Start is at the direct block level, free

			 * everything to the end of the level.

			 */

			ext4_free_data(handle, inode, NULL, i_data + offsets[0],

				       i_data + EXT4_NDIR_BLOCKS);

			goto end_range;

		}

			if (first > offset) {

				first2 = first - offset;

				count2 = count;





		partial = ext4_find_shared(inode, n, offsets, chain, &nr);

		if (nr) {

			if (partial == chain) {

				/* Shared branch grows from the inode */

				ext4_free_branches(handle, inode, NULL,

					   &nr, &nr+1, (chain+n-1) - partial);

				*partial->p = 0;

			} else {

				first2 = 0;

				count2 = count - (offset - first);

				/* Shared branch grows from an indirect block */

				BUFFER_TRACE(partial->bh, "get_write_access");

				ext4_free_branches(handle, inode, partial->bh,

					partial->p,

					partial->p+1, (chain+n-1) - partial);

			}

			ret = free_hole_blocks(handle, inode, bh,

					       (__le32 *)bh->b_data, level - 1,

					       first2, count2,

					       inode->i_sb->s_blocksize >> 2);

			if (ret) {

				brelse(bh);

				goto err;

		}



		/*

		 * Clear the ends of indirect blocks on the shared branch

		 * at the start of the range

		 */

		while (partial > chain) {

			ext4_free_branches(handle, inode, partial->bh,

				partial->p + 1,

				(__le32 *)partial->bh->b_data+addr_per_block,

				(chain+n-1) - partial);

			BUFFER_TRACE(partial->bh, "call brelse");

			brelse(partial->bh);

			partial--;

		}

		if (level == 0 ||

		    (bh && all_zeroes((__le32 *)bh->b_data,

				      (__le32 *)bh->b_data + addr_per_block))) {

			ext4_free_data(handle, inode, parent_bh,

				       i_data, i_data + 1);



end_range:

		partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);

		if (nr2) {

			if (partial2 == chain2) {

				/*

				 * Remember, end is exclusive so here we're at

				 * the start of the next level we're not going

				 * to free. Everything was covered by the start

				 * of the range.

				 */

				return 0;

			} else {

				/* Shared branch grows from an indirect block */

				partial2--;

			}

		brelse(bh);

		bh = NULL;

		} else {

			/*

			 * ext4_find_shared returns Indirect structure which

			 * points to the last element which should not be

			 * removed by truncate. But this is end of the range

			 * in punch_hole so we need to point to the next element

			 */

			partial2->p++;

		}



err:

	return ret;

		/*

		 * Clear the ends of indirect blocks on the shared branch

		 * at the end of the range

		 */

		while (partial2 > chain2) {

			ext4_free_branches(handle, inode, partial2->bh,

					   (__le32 *)partial2->bh->b_data,

					   partial2->p,

					   (chain2+n2-1) - partial2);

			BUFFER_TRACE(partial2->bh, "call brelse");

			brelse(partial2->bh);

			partial2--;

		}

		goto do_indirects;

	}



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);

	int level, ret = 0;

	int num = EXT4_NDIR_BLOCKS;

	ext4_lblk_t count, max = EXT4_NDIR_BLOCKS;

	__le32 *i_data = EXT4_I(inode)->i_data;



	count = stop - first;

	for (level = 0; level < 4; level++, max *= addr_per_block) {

		if (first < max) {

			ret = free_hole_blocks(handle, inode, NULL, i_data,

					       level, first, count, num);

			if (ret)

				goto err;

			if (count > max - first)

				count -= max - first;

			else

				break;

			first = 0;

		} else {

			first -= max;

	/* Punch happened within the same level (n == n2) */

	partial = ext4_find_shared(inode, n, offsets, chain, &nr);

	partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);

	/*

	 * ext4_find_shared returns Indirect structure which

	 * points to the last element which should not be

	 * removed by truncate. But this is end of the range

	 * in punch_hole so we need to point to the next element

	 */

	partial2->p++;

	while ((partial > chain) || (partial2 > chain2)) {

		/* We're at the same block, so we're almost finished */

		if ((partial->bh && partial2->bh) &&

		    (partial->bh->b_blocknr == partial2->bh->b_blocknr)) {

			if ((partial > chain) && (partial2 > chain2)) {

				ext4_free_branches(handle, inode, partial->bh,

						   partial->p + 1,

						   partial2->p,

						   (chain+n-1) - partial);

				BUFFER_TRACE(partial->bh, "call brelse");

				brelse(partial->bh);

				BUFFER_TRACE(partial2->bh, "call brelse");

				brelse(partial2->bh);

			}

		i_data += num;

		if (level == 0) {

			num = 1;

			max = 1;

			return 0;

		}

		/*

		 * Clear the ends of indirect blocks on the shared branch

		 * at the start of the range

		 */

		if (partial > chain) {

			ext4_free_branches(handle, inode, partial->bh,

				   partial->p + 1,

				   (__le32 *)partial->bh->b_data+addr_per_block,

				   (chain+n-1) - partial);

			BUFFER_TRACE(partial->bh, "call brelse");

			brelse(partial->bh);

			partial--;

		}

		/*

		 * Clear the ends of indirect blocks on the shared branch

		 * at the end of the range

		 */

		if (partial2 > chain2) {

			ext4_free_branches(handle, inode, partial2->bh,

					   (__le32 *)partial2->bh->b_data,

					   partial2->p,

					   (chain2+n-1) - partial2);

			BUFFER_TRACE(partial2->bh, "call brelse");

			brelse(partial2->bh);

			partial2--;

		}



err:

	return ret;

	}



do_indirects:

	/* Kill the remaining (whole) subtrees */

	switch (offsets[0]) {

	default:

		if (++n >= n2)

			return 0;

		nr = i_data[EXT4_IND_BLOCK];

		if (nr) {

			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);

			i_data[EXT4_IND_BLOCK] = 0;

		}

	case EXT4_IND_BLOCK:

		if (++n >= n2)

			return 0;

		nr = i_data[EXT4_DIND_BLOCK];

		if (nr) {

			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);

			i_data[EXT4_DIND_BLOCK] = 0;

		}

	case EXT4_DIND_BLOCK:

		if (++n >= n2)

			return 0;

		nr = i_data[EXT4_TIND_BLOCK];

		if (nr) {

			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);

			i_data[EXT4_TIND_BLOCK] = 0;

		}

	case EXT4_TIND_BLOCK:

		;

	}

	return 0;

}

fs/ext4/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -3506,7 +3506,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length) 
		ret = ext4_ext_remove_space(inode, first_block,

					    stop_block - 1);

	else

		ret = ext4_free_hole_blocks(handle, inode, first_block,

		ret = ext4_ind_remove_space(handle, inode, first_block,

					    stop_block);



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

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