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Commit b05e6ae5 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: drop ec_type from the ext4_ext_cache structure 



We can encode the ec_type information by using ee_len == 0 to denote
EXT4_EXT_CACHE_NO, ee_start == 0 to denote EXT4_EXT_CACHE_GAP, and if
neither is true, then the cache type must be EXT4_EXT_CACHE_EXTENT.
This allows us to reduce the size of ext4_ext_inode by another 8
bytes.  (ec_type is 4 bytes, plus another 4 bytes of padding)

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 01f49d0b

fs/ext4/ext4.h

+2 −1
Original line number Diff line number Diff line
@@ -738,12 +738,13 @@ do { \ 


/*

 * storage for cached extent

 * If ec_len == 0, then the cache is invalid.

 * If ec_start == 0, then the cache represents a gap (null mapping)

 */

struct ext4_ext_cache {

	ext4_fsblk_t	ec_start;

	ext4_lblk_t	ec_block;

	__u32		ec_len; /* must be 32bit to return holes */

	__u32		ec_type;

};



/*

fs/ext4/ext4_extents.h

+1 −5
Original line number Diff line number Diff line
@@ -119,10 +119,6 @@ struct ext4_ext_path { 
 * structure for external API

 */



#define EXT4_EXT_CACHE_NO	0

#define EXT4_EXT_CACHE_GAP	1

#define EXT4_EXT_CACHE_EXTENT	2



/*

 * to be called by ext4_ext_walk_space()

 * negative retcode - error
@@ -197,7 +193,7 @@ static inline unsigned short ext_depth(struct inode *inode) 
static inline void

ext4_ext_invalidate_cache(struct inode *inode)

{

	EXT4_I(inode)->i_cached_extent.ec_type = EXT4_EXT_CACHE_NO;

	EXT4_I(inode)->i_cached_extent.ec_len = 0;

}



static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext)

fs/ext4/extents.c

+15 −22
Original line number Diff line number Diff line
@@ -1894,12 +1894,10 @@ static int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block, 
			cbex.ec_block = start;

			cbex.ec_len = end - start;

			cbex.ec_start = 0;

			cbex.ec_type = EXT4_EXT_CACHE_GAP;

		} else {

			cbex.ec_block = le32_to_cpu(ex->ee_block);

			cbex.ec_len = ext4_ext_get_actual_len(ex);

			cbex.ec_start = ext4_ext_pblock(ex);

			cbex.ec_type = EXT4_EXT_CACHE_EXTENT;

		}



		if (unlikely(cbex.ec_len == 0)) {
@@ -1939,13 +1937,12 @@ static int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block, 


static void

ext4_ext_put_in_cache(struct inode *inode, ext4_lblk_t block,

			__u32 len, ext4_fsblk_t start, int type)

			__u32 len, ext4_fsblk_t start)

{

	struct ext4_ext_cache *cex;

	BUG_ON(len == 0);

	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);

	cex = &EXT4_I(inode)->i_cached_extent;

	cex->ec_type = type;

	cex->ec_block = block;

	cex->ec_len = len;

	cex->ec_start = start;
@@ -1998,15 +1995,18 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path, 
	}



	ext_debug(" -> %u:%lu\n", lblock, len);

	ext4_ext_put_in_cache(inode, lblock, len, 0, EXT4_EXT_CACHE_GAP);

	ext4_ext_put_in_cache(inode, lblock, len, 0);

}



/*

 * Return 0 if cache is invalid; 1 if the cache is valid

 */

static int

ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,

			struct ext4_extent *ex)

{

	struct ext4_ext_cache *cex;

	int ret = EXT4_EXT_CACHE_NO;

	int ret = 0;



	/*

	 * We borrow i_block_reservation_lock to protect i_cached_extent
@@ -2015,11 +2015,9 @@ ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block, 
	cex = &EXT4_I(inode)->i_cached_extent;



	/* has cache valid data? */

	if (cex->ec_type == EXT4_EXT_CACHE_NO)

	if (cex->ec_len == 0)

		goto errout;



	BUG_ON(cex->ec_type != EXT4_EXT_CACHE_GAP &&

			cex->ec_type != EXT4_EXT_CACHE_EXTENT);

	if (in_range(block, cex->ec_block, cex->ec_len)) {

		ex->ee_block = cpu_to_le32(cex->ec_block);

		ext4_ext_store_pblock(ex, cex->ec_start);
@@ -2027,7 +2025,7 @@ ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block, 
		ext_debug("%u cached by %u:%u:%llu\n",

				block,

				cex->ec_block, cex->ec_len, cex->ec_start);

		ret = cex->ec_type;

		ret = 1;

	}

errout:

	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
@@ -3298,7 +3296,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
	struct ext4_extent_header *eh;

	struct ext4_extent newex, *ex;

	ext4_fsblk_t newblock;

	int err = 0, depth, ret, cache_type;

	int err = 0, depth, ret;

	unsigned int allocated = 0;

	struct ext4_allocation_request ar;

	ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio;
@@ -3307,9 +3305,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
		  map->m_lblk, map->m_len, inode->i_ino);



	/* check in cache */

	cache_type = ext4_ext_in_cache(inode, map->m_lblk, &newex);

	if (cache_type) {

		if (cache_type == EXT4_EXT_CACHE_GAP) {

	if (ext4_ext_in_cache(inode, map->m_lblk, &newex)) {

		if (!newex.ee_start_lo && !newex.ee_start_hi) {

			if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {

				/*

				 * block isn't allocated yet and
@@ -3318,7 +3315,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
				goto out2;

			}

			/* we should allocate requested block */

		} else if (cache_type == EXT4_EXT_CACHE_EXTENT) {

		} else {

			/* block is already allocated */

			newblock = map->m_lblk

				   - le32_to_cpu(newex.ee_block)
@@ -3327,8 +3324,6 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
			allocated = ext4_ext_get_actual_len(&newex) -

				(map->m_lblk - le32_to_cpu(newex.ee_block));

			goto out;

		} else {

			BUG();

		}

	}
@@ -3379,8 +3374,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
			/* Do not put uninitialized extent in the cache */

			if (!ext4_ext_is_uninitialized(ex)) {

				ext4_ext_put_in_cache(inode, ee_block,

							ee_len, ee_start,

							EXT4_EXT_CACHE_EXTENT);

							ee_len, ee_start);

				goto out;

			}

			ret = ext4_ext_handle_uninitialized_extents(handle,
@@ -3512,8 +3506,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
	 * when it is _not_ an uninitialized extent.

	 */

	if ((flags & EXT4_GET_BLOCKS_UNINIT_EXT) == 0) {

		ext4_ext_put_in_cache(inode, map->m_lblk, allocated, newblock,

						EXT4_EXT_CACHE_EXTENT);

		ext4_ext_put_in_cache(inode, map->m_lblk, allocated, newblock);

		ext4_update_inode_fsync_trans(handle, inode, 1);

	} else

		ext4_update_inode_fsync_trans(handle, inode, 0);
@@ -3789,7 +3782,7 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path, 


	logical =  (__u64)newex->ec_block << blksize_bits;



	if (newex->ec_type == EXT4_EXT_CACHE_GAP) {

	if (newex->ec_start == 0) {

		pgoff_t offset;

		struct page *page;

		struct buffer_head *bh = NULL;