ext4: Convert callers of ext4_get_blocks() to use ext4_map_blocks()

This saves a huge amount of stack space by avoiding unnecesary struct
buffer_head's from being allocated on the stack.

In addition, to make the code easier to understand, collapse and
refactor ext4_get_block(), ext4_get_block_write(),
noalloc_get_block_write(), into a single function.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 127 insertions, 200 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ff2f5fd681b5..0b1d7c89f93f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1336,133 +1336,112 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 	return retval;
 }
 
-int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
-		    unsigned int max_blocks, struct buffer_head *bh,
-		    int flags)
-{
-	struct ext4_map_blocks map;
-	int ret;
-
-	map.m_lblk = block;
-	map.m_len = max_blocks;
-
-	ret = ext4_map_blocks(handle, inode, &map, flags);
-	if (ret < 0)
-		return ret;
-
-	bh->b_blocknr = map.m_pblk;
-	bh->b_size = inode->i_sb->s_blocksize * map.m_len;
-	bh->b_bdev = inode->i_sb->s_bdev;
-	bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
-	return ret;
-}
-
 /* Maximum number of blocks we map for direct IO at once. */
 #define DIO_MAX_BLOCKS 4096
 
-int ext4_get_block(struct inode *inode, sector_t iblock,
-		   struct buffer_head *bh_result, int create)
+static int _ext4_get_block(struct inode *inode, sector_t iblock,
+			   struct buffer_head *bh, int flags)
 {
 	handle_t *handle = ext4_journal_current_handle();
+	struct ext4_map_blocks map;
 	int ret = 0, started = 0;
-	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
 	int dio_credits;
 
-	if (create && !handle) {
+	map.m_lblk = iblock;
+	map.m_len = bh->b_size >> inode->i_blkbits;
+
+	if (flags && !handle) {
 		/* Direct IO write... */
-		if (max_blocks > DIO_MAX_BLOCKS)
-			max_blocks = DIO_MAX_BLOCKS;
-		dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
+		if (map.m_len > DIO_MAX_BLOCKS)
+			map.m_len = DIO_MAX_BLOCKS;
+		dio_credits = ext4_chunk_trans_blocks(inode, map.m_len);
 		handle = ext4_journal_start(inode, dio_credits);
 		if (IS_ERR(handle)) {
 			ret = PTR_ERR(handle);
-			goto out;
+			return ret;
 		}
 		started = 1;
 	}
 
-	ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
-			      create ? EXT4_GET_BLOCKS_CREATE : 0);
+	ret = ext4_map_blocks(handle, inode, &map, flags);
 	if (ret > 0) {
-		bh_result->b_size = (ret << inode->i_blkbits);
+		map_bh(bh, inode->i_sb, map.m_pblk);
+		bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
 		ret = 0;
 	}
 	if (started)
 		ext4_journal_stop(handle);
-out:
 	return ret;
 }
 
+int ext4_get_block(struct inode *inode, sector_t iblock,
+		   struct buffer_head *bh, int create)
+{
+	return _ext4_get_block(inode, iblock, bh,
+			       create ? EXT4_GET_BLOCKS_CREATE : 0);
+}
+
 /*
  * `handle' can be NULL if create is zero
  */
 struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
 				ext4_lblk_t block, int create, int *errp)
 {
-	struct buffer_head dummy;
+	struct ext4_map_blocks map;
+	struct buffer_head *bh;
 	int fatal = 0, err;
-	int flags = 0;
 
 	J_ASSERT(handle != NULL || create == 0);
 
-	dummy.b_state = 0;
-	dummy.b_blocknr = -1000;
-	buffer_trace_init(&dummy.b_history);
-	if (create)
-		flags |= EXT4_GET_BLOCKS_CREATE;
-	err = ext4_get_blocks(handle, inode, block, 1, &dummy, flags);
-	/*
-	 * ext4_get_blocks() returns number of blocks mapped. 0 in
-	 * case of a HOLE.
-	 */
-	if (err > 0) {
-		if (err > 1)
-			WARN_ON(1);
-		err = 0;
+	map.m_lblk = block;
+	map.m_len = 1;
+	err = ext4_map_blocks(handle, inode, &map,
+			      create ? EXT4_GET_BLOCKS_CREATE : 0);
+
+	if (err < 0)
+		*errp = err;
+	if (err <= 0)
+		return NULL;
+	*errp = 0;
+
+	bh = sb_getblk(inode->i_sb, map.m_pblk);
+	if (!bh) {
+		*errp = -EIO;
+		return NULL;
 	}
-	*errp = err;
-	if (!err && buffer_mapped(&dummy)) {
-		struct buffer_head *bh;
-		bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
-		if (!bh) {
-			*errp = -EIO;
-			goto err;
-		}
-		if (buffer_new(&dummy)) {
-			J_ASSERT(create != 0);
-			J_ASSERT(handle != NULL);
+	if (map.m_flags & EXT4_MAP_NEW) {
+		J_ASSERT(create != 0);
+		J_ASSERT(handle != NULL);
 
-			/*
-			 * Now that we do not always journal data, we should
-			 * keep in mind whether this should always journal the
-			 * new buffer as metadata.  For now, regular file
-			 * writes use ext4_get_block instead, so it's not a
-			 * problem.
-			 */
-			lock_buffer(bh);
-			BUFFER_TRACE(bh, "call get_create_access");
-			fatal = ext4_journal_get_create_access(handle, bh);
-			if (!fatal && !buffer_uptodate(bh)) {
-				memset(bh->b_data, 0, inode->i_sb->s_blocksize);
-				set_buffer_uptodate(bh);
-			}
-			unlock_buffer(bh);
-			BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
-			err = ext4_handle_dirty_metadata(handle, inode, bh);
-			if (!fatal)
-				fatal = err;
-		} else {
-			BUFFER_TRACE(bh, "not a new buffer");
-		}
-		if (fatal) {
-			*errp = fatal;
-			brelse(bh);
-			bh = NULL;
+		/*
+		 * Now that we do not always journal data, we should
+		 * keep in mind whether this should always journal the
+		 * new buffer as metadata.  For now, regular file
+		 * writes use ext4_get_block instead, so it's not a
+		 * problem.
+		 */
+		lock_buffer(bh);
+		BUFFER_TRACE(bh, "call get_create_access");
+		fatal = ext4_journal_get_create_access(handle, bh);
+		if (!fatal && !buffer_uptodate(bh)) {
+			memset(bh->b_data, 0, inode->i_sb->s_blocksize);
+			set_buffer_uptodate(bh);
 		}
-		return bh;
+		unlock_buffer(bh);
+		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
+		err = ext4_handle_dirty_metadata(handle, inode, bh);
+		if (!fatal)
+			fatal = err;
+	} else {
+		BUFFER_TRACE(bh, "not a new buffer");
 	}
-err:
-	return NULL;
+	if (fatal) {
+		*errp = fatal;
+		brelse(bh);
+		bh = NULL;
+	}
+	return bh;
 }
 
 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
@@ -2050,28 +2029,23 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
 /*
  * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
  *
- * @mpd->inode - inode to walk through
- * @exbh->b_blocknr - first block on a disk
- * @exbh->b_size - amount of space in bytes
- * @logical - first logical block to start assignment with
- *
  * the function goes through all passed space and put actual disk
  * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
  */
-static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
-				 struct buffer_head *exbh)
+static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd,
+				 struct ext4_map_blocks *map)
 {
 	struct inode *inode = mpd->inode;
 	struct address_space *mapping = inode->i_mapping;
-	int blocks = exbh->b_size >> inode->i_blkbits;
-	sector_t pblock = exbh->b_blocknr, cur_logical;
+	int blocks = map->m_len;
+	sector_t pblock = map->m_pblk, cur_logical;
 	struct buffer_head *head, *bh;
 	pgoff_t index, end;
 	struct pagevec pvec;
 	int nr_pages, i;
 
-	index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
-	end = (logical + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	index = map->m_lblk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	end = (map->m_lblk + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
 	cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
 
 	pagevec_init(&pvec, 0);
@@ -2098,17 +2072,16 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
 
 			/* skip blocks out of the range */
 			do {
-				if (cur_logical >= logical)
+				if (cur_logical >= map->m_lblk)
 					break;
 				cur_logical++;
 			} while ((bh = bh->b_this_page) != head);
 
 			do {
-				if (cur_logical >= logical + blocks)
+				if (cur_logical >= map->m_lblk + blocks)
 					break;
 
-				if (buffer_delay(bh) ||
-						buffer_unwritten(bh)) {
+				if (buffer_delay(bh) || buffer_unwritten(bh)) {
 
 					BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
 
@@ -2127,7 +2100,7 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
 				} else if (buffer_mapped(bh))
 					BUG_ON(bh->b_blocknr != pblock);
 
-				if (buffer_uninit(exbh))
+				if (map->m_flags & EXT4_MAP_UNINIT)
 					set_buffer_uninit(bh);
 				cur_logical++;
 				pblock++;
@@ -2138,21 +2111,6 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
 }
 
 
-/*
- * __unmap_underlying_blocks - just a helper function to unmap
- * set of blocks described by @bh
- */
-static inline void __unmap_underlying_blocks(struct inode *inode,
-					     struct buffer_head *bh)
-{
-	struct block_device *bdev = inode->i_sb->s_bdev;
-	int blocks, i;
-
-	blocks = bh->b_size >> inode->i_blkbits;
-	for (i = 0; i < blocks; i++)
-		unmap_underlying_metadata(bdev, bh->b_blocknr + i);
-}
-
 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
 					sector_t logical, long blk_cnt)
 {
@@ -2214,7 +2172,7 @@ static void ext4_print_free_blocks(struct inode *inode)
 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 {
 	int err, blks, get_blocks_flags;
-	struct buffer_head new;
+	struct ext4_map_blocks map;
 	sector_t next = mpd->b_blocknr;
 	unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
 	loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
@@ -2255,15 +2213,15 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 	 * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
 	 * variables are updated after the blocks have been allocated.
 	 */
-	new.b_state = 0;
+	map.m_lblk = next;
+	map.m_len = max_blocks;
 	get_blocks_flags = EXT4_GET_BLOCKS_CREATE;
 	if (ext4_should_dioread_nolock(mpd->inode))
 		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
 	if (mpd->b_state & (1 << BH_Delay))
 		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;
 
-	blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
-			       &new, get_blocks_flags);
+	blks = ext4_map_blocks(handle, mpd->inode, &map, get_blocks_flags);
 	if (blks < 0) {
 		err = blks;
 		/*
@@ -2305,10 +2263,13 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 	}
 	BUG_ON(blks == 0);
 
-	new.b_size = (blks << mpd->inode->i_blkbits);
+	if (map.m_flags & EXT4_MAP_NEW) {
+		struct block_device *bdev = mpd->inode->i_sb->s_bdev;
+		int i;
 
-	if (buffer_new(&new))
-		__unmap_underlying_blocks(mpd->inode, &new);
+		for (i = 0; i < map.m_len; i++)
+			unmap_underlying_metadata(bdev, map.m_pblk + i);
+	}
 
 	/*
 	 * If blocks are delayed marked, we need to
@@ -2316,7 +2277,7 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 	 */
 	if ((mpd->b_state & (1 << BH_Delay)) ||
 	    (mpd->b_state & (1 << BH_Unwritten)))
-		mpage_put_bnr_to_bhs(mpd, next, &new);
+		mpage_put_bnr_to_bhs(mpd, &map);
 
 	if (ext4_should_order_data(mpd->inode)) {
 		err = ext4_jbd2_file_inode(handle, mpd->inode);
@@ -2534,8 +2495,9 @@ static int __mpage_da_writepage(struct page *page,
  * initialized properly.
  */
 static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
-				  struct buffer_head *bh_result, int create)
+				  struct buffer_head *bh, int create)
 {
+	struct ext4_map_blocks map;
 	int ret = 0;
 	sector_t invalid_block = ~((sector_t) 0xffff);
 
@@ -2543,16 +2505,22 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 		invalid_block = ~0;
 
 	BUG_ON(create == 0);
-	BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
+	BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
+
+	map.m_lblk = iblock;
+	map.m_len = 1;
 
 	/*
 	 * first, we need to know whether the block is allocated already
 	 * preallocated blocks are unmapped but should treated
 	 * the same as allocated blocks.
 	 */
-	ret = ext4_get_blocks(NULL, inode, iblock, 1,  bh_result, 0);
-	if ((ret == 0) && !buffer_delay(bh_result)) {
-		/* the block isn't (pre)allocated yet, let's reserve space */
+	ret = ext4_map_blocks(NULL, inode, &map, 0);
+	if (ret < 0)
+		return ret;
+	if (ret == 0) {
+		if (buffer_delay(bh))
+			return 0; /* Not sure this could or should happen */
 		/*
 		 * XXX: __block_prepare_write() unmaps passed block,
 		 * is it OK?
@@ -2562,26 +2530,26 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 			/* not enough space to reserve */
 			return ret;
 
-		map_bh(bh_result, inode->i_sb, invalid_block);
-		set_buffer_new(bh_result);
-		set_buffer_delay(bh_result);
-	} else if (ret > 0) {
-		bh_result->b_size = (ret << inode->i_blkbits);
-		if (buffer_unwritten(bh_result)) {
-			/* A delayed write to unwritten bh should
-			 * be marked new and mapped.  Mapped ensures
-			 * that we don't do get_block multiple times
-			 * when we write to the same offset and new
-			 * ensures that we do proper zero out for
-			 * partial write.
-			 */
-			set_buffer_new(bh_result);
-			set_buffer_mapped(bh_result);
-		}
-		ret = 0;
+		map_bh(bh, inode->i_sb, invalid_block);
+		set_buffer_new(bh);
+		set_buffer_delay(bh);
+		return 0;
 	}
 
-	return ret;
+	map_bh(bh, inode->i_sb, map.m_pblk);
+	bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+
+	if (buffer_unwritten(bh)) {
+		/* A delayed write to unwritten bh should be marked
+		 * new and mapped.  Mapped ensures that we don't do
+		 * get_block multiple times when we write to the same
+		 * offset and new ensures that we do proper zero out
+		 * for partial write.
+		 */
+		set_buffer_new(bh);
+		set_buffer_mapped(bh);
+	}
+	return 0;
 }
 
 /*
@@ -2603,21 +2571,8 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
 				   struct buffer_head *bh_result, int create)
 {
-	int ret = 0;
-	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
-
 	BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
-
-	/*
-	 * we don't want to do block allocation in writepage
-	 * so call get_block_wrap with create = 0
-	 */
-	ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
-	if (ret > 0) {
-		bh_result->b_size = (ret << inode->i_blkbits);
-		ret = 0;
-	}
-	return ret;
+	return _ext4_get_block(inode, iblock, bh_result, 0);
 }
 
 static int bget_one(handle_t *handle, struct buffer_head *bh)
@@ -3644,46 +3599,18 @@ out:
 	return ret;
 }
 
+/*
+ * ext4_get_block used when preparing for a DIO write or buffer write.
+ * We allocate an uinitialized extent if blocks haven't been allocated.
+ * The extent will be converted to initialized after the IO is complete.
+ */
 static int ext4_get_block_write(struct inode *inode, sector_t iblock,
 		   struct buffer_head *bh_result, int create)
 {
-	handle_t *handle = ext4_journal_current_handle();
-	int ret = 0;
-	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
-	int dio_credits;
-	int started = 0;
-
 	ext4_debug("ext4_get_block_write: inode %lu, create flag %d\n",
 		   inode->i_ino, create);
-	/*
-	 * ext4_get_block in prepare for a DIO write or buffer write.
-	 * We allocate an uinitialized extent if blocks haven't been allocated.
-	 * The extent will be converted to initialized after IO complete.
-	 */
-	create = EXT4_GET_BLOCKS_IO_CREATE_EXT;
-
-	if (!handle) {
-		if (max_blocks > DIO_MAX_BLOCKS)
-			max_blocks = DIO_MAX_BLOCKS;
-		dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
-		handle = ext4_journal_start(inode, dio_credits);
-		if (IS_ERR(handle)) {
-			ret = PTR_ERR(handle);
-			goto out;
-		}
-		started = 1;
-	}
-
-	ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
-			      create);
-	if (ret > 0) {
-		bh_result->b_size = (ret << inode->i_blkbits);
-		ret = 0;
-	}
-	if (started)
-		ext4_journal_stop(handle);
-out:
-	return ret;
+	return _ext4_get_block(inode, iblock, bh_result,
+			       EXT4_GET_BLOCKS_IO_CREATE_EXT);
 }
 
 static void dump_completed_IO(struct inode * inode)