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Commit d100eef2 authored by Zheng Liu's avatar Zheng Liu Committed by Theodore Ts'o
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ext4: lookup block mapping in extent status tree 



After tracking all extent status, we already have a extent cache in
memory.  Every time we want to lookup a block mapping, we can first
try to lookup it in extent status tree to avoid a potential disk I/O.

A new function called ext4_es_lookup_extent is defined to finish this
work.  When we try to lookup a block mapping, we always call
ext4_map_blocks and/or ext4_da_map_blocks.  So in these functions we
first try to lookup a block mapping in extent status tree.

A new flag EXT4_GET_BLOCKS_NO_PUT_HOLE is used in ext4_da_map_blocks
in order not to put a hole into extent status tree because this hole
will be converted to delayed extent in the tree immediately.

Signed-off-by: default avatarZheng Liu <wenqing.lz@taobao.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: Jan kara <jack@suse.cz>
parent f7fec032

fs/ext4/ext4.h

+2 −0
Original line number Diff line number Diff line
@@ -579,6 +579,8 @@ enum { 
#define EXT4_GET_BLOCKS_KEEP_SIZE		0x0080

	/* Do not take i_data_sem locking in ext4_map_blocks */

#define EXT4_GET_BLOCKS_NO_LOCK			0x0100

	/* Do not put hole in extent cache */

#define EXT4_GET_BLOCKS_NO_PUT_HOLE		0x0200



/*

 * Flags used by ext4_free_blocks

fs/ext4/extents.c

+8 −1
Original line number Diff line number Diff line
@@ -2167,6 +2167,9 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path, 
				block,

				le32_to_cpu(ex->ee_block),

				 ext4_ext_get_actual_len(ex));

		if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))

			ext4_es_insert_extent(inode, lblock, len, ~0,

					      EXTENT_STATUS_HOLE);

	} else if (block >= le32_to_cpu(ex->ee_block)

			+ ext4_ext_get_actual_len(ex)) {

		ext4_lblk_t next;
@@ -2180,6 +2183,9 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path, 
				block);

		BUG_ON(next == lblock);

		len = next - lblock;

		if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))

			ext4_es_insert_extent(inode, lblock, len, ~0,

					      EXTENT_STATUS_HOLE);

	} else {

		lblock = len = 0;

		BUG();
@@ -4018,6 +4024,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
		 * put just found gap into cache to speed up

		 * subsequent requests

		 */

		if ((flags & EXT4_GET_BLOCKS_NO_PUT_HOLE) == 0)

			ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);

		goto out2;

	}

fs/ext4/extents_status.c

+60 −0
Original line number Diff line number Diff line
@@ -461,6 +461,66 @@ error: 
	return err;

}



/*

 * ext4_es_lookup_extent() looks up an extent in extent status tree.

 *

 * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.

 *

 * Return: 1 on found, 0 on not

 */

int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,

			  struct extent_status *es)

{

	struct ext4_es_tree *tree;

	struct extent_status *es1 = NULL;

	struct rb_node *node;

	int found = 0;



	trace_ext4_es_lookup_extent_enter(inode, lblk);

	es_debug("lookup extent in block %u\n", lblk);



	tree = &EXT4_I(inode)->i_es_tree;

	read_lock(&EXT4_I(inode)->i_es_lock);



	/* find extent in cache firstly */

	es->es_lblk = es->es_len = es->es_pblk = 0;

	if (tree->cache_es) {

		es1 = tree->cache_es;

		if (in_range(lblk, es1->es_lblk, es1->es_len)) {

			es_debug("%u cached by [%u/%u)\n",

				 lblk, es1->es_lblk, es1->es_len);

			found = 1;

			goto out;

		}

	}



	node = tree->root.rb_node;

	while (node) {

		es1 = rb_entry(node, struct extent_status, rb_node);

		if (lblk < es1->es_lblk)

			node = node->rb_left;

		else if (lblk > ext4_es_end(es1))

			node = node->rb_right;

		else {

			found = 1;

			break;

		}

	}



out:

	if (found) {

		BUG_ON(!es1);

		es->es_lblk = es1->es_lblk;

		es->es_len = es1->es_len;

		es->es_pblk = es1->es_pblk;

	}



	read_unlock(&EXT4_I(inode)->i_es_lock);



	trace_ext4_es_lookup_extent_exit(inode, es, found);

	return found;

}



static int __es_remove_extent(struct ext4_es_tree *tree, ext4_lblk_t lblk,

				 ext4_lblk_t end)

{

fs/ext4/extents_status.h

+2 −0
Original line number Diff line number Diff line
@@ -53,6 +53,8 @@ extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk, 
				 ext4_lblk_t len);

extern void ext4_es_find_delayed_extent(struct inode *inode, ext4_lblk_t lblk,

					struct extent_status *es);

extern int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,

				 struct extent_status *es);



static inline int ext4_es_is_written(struct extent_status *es)

{

fs/ext4/inode.c

+64 −2
Original line number Diff line number Diff line
@@ -507,12 +507,33 @@ static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx, 
int ext4_map_blocks(handle_t *handle, struct inode *inode,

		    struct ext4_map_blocks *map, int flags)

{

	struct extent_status es;

	int retval;



	map->m_flags = 0;

	ext_debug("ext4_map_blocks(): inode %lu, flag %d, max_blocks %u,"

		  "logical block %lu\n", inode->i_ino, flags, map->m_len,

		  (unsigned long) map->m_lblk);



	/* Lookup extent status tree firstly */

	if (ext4_es_lookup_extent(inode, map->m_lblk, &es)) {

		if (ext4_es_is_written(&es) || ext4_es_is_unwritten(&es)) {

			map->m_pblk = ext4_es_pblock(&es) +

					map->m_lblk - es.es_lblk;

			map->m_flags |= ext4_es_is_written(&es) ?

					EXT4_MAP_MAPPED : EXT4_MAP_UNWRITTEN;

			retval = es.es_len - (map->m_lblk - es.es_lblk);

			if (retval > map->m_len)

				retval = map->m_len;

			map->m_len = retval;

		} else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) {

			retval = 0;

		} else {

			BUG_ON(1);

		}

		goto found;

	}



	/*

	 * Try to see if we can get the block without requesting a new

	 * file system block.
@@ -544,6 +565,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

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



found:

	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {

		int ret = check_block_validity(inode, map);

		if (ret != 0)
@@ -1743,6 +1765,7 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock, 
			      struct ext4_map_blocks *map,

			      struct buffer_head *bh)

{

	struct extent_status es;

	int retval;

	sector_t invalid_block = ~((sector_t) 0xffff);
@@ -1753,6 +1776,42 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock, 
	ext_debug("ext4_da_map_blocks(): inode %lu, max_blocks %u,"

		  "logical block %lu\n", inode->i_ino, map->m_len,

		  (unsigned long) map->m_lblk);



	/* Lookup extent status tree firstly */

	if (ext4_es_lookup_extent(inode, iblock, &es)) {



		if (ext4_es_is_hole(&es)) {

			retval = 0;

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

			goto add_delayed;

		}



		/*

		 * Delayed extent could be allocated by fallocate.

		 * So we need to check it.

		 */

		if (ext4_es_is_delayed(&es) && !ext4_es_is_unwritten(&es)) {

			map_bh(bh, inode->i_sb, invalid_block);

			set_buffer_new(bh);

			set_buffer_delay(bh);

			return 0;

		}



		map->m_pblk = ext4_es_pblock(&es) + iblock - es.es_lblk;

		retval = es.es_len - (iblock - es.es_lblk);

		if (retval > map->m_len)

			retval = map->m_len;

		map->m_len = retval;

		if (ext4_es_is_written(&es))

			map->m_flags |= EXT4_MAP_MAPPED;

		else if (ext4_es_is_unwritten(&es))

			map->m_flags |= EXT4_MAP_UNWRITTEN;

		else

			BUG_ON(1);



		return retval;

	}



	/*

	 * Try to see if we can get the block without requesting a new

	 * file system block.
@@ -1771,10 +1830,13 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock, 
			map->m_flags |= EXT4_MAP_FROM_CLUSTER;

		retval = 0;

	} else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		retval = ext4_ext_map_blocks(NULL, inode, map, 0);

		retval = ext4_ext_map_blocks(NULL, inode, map,

					     EXT4_GET_BLOCKS_NO_PUT_HOLE);

	else

		retval = ext4_ind_map_blocks(NULL, inode, map, 0);

		retval = ext4_ind_map_blocks(NULL, inode, map,

					     EXT4_GET_BLOCKS_NO_PUT_HOLE);



add_delayed:

	if (retval == 0) {

		int ret;

		/*