[PATCH v2 04/10] ext4: refactor ext4_zero_range()

[Zhang Yi <yi.zhang@huaweicloud.com>]

From: Zhang Yi <yi.zhang@huawei.com>

Current ext4_zero_range() is full of complex position calculation and
stale error out tags. In order to clean up the code and make things
clear, refactor it by a) simplify and rename variables, b) remove some
unnecessary position calculations, always write back dirty data and
drop cache from offset to end, instead of only write back aligned
blocks, c) rename the stale out_mutex tag.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/extents.c | 96 ++++++++++++++++++-----------------------------
 1 file changed, 37 insertions(+), 59 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index d9fccf2970e9..2fb0c2e303c7 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4540,40 +4540,15 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	struct inode *inode = file_inode(file);
 	struct address_space *mapping = file->f_mapping;
 	handle_t *handle = NULL;
-	unsigned int max_blocks;
 	loff_t new_size = 0;
-	int ret = 0;
-	int flags;
-	int credits;
-	int partial_begin, partial_end;
-	loff_t start, end;
-	ext4_lblk_t lblk;
+	loff_t end = offset + len;
+	ext4_lblk_t start_lblk, end_lblk;
+	unsigned int blocksize = i_blocksize(inode);
 	unsigned int blkbits = inode->i_blkbits;
+	int ret, flags, credits;
 
 	trace_ext4_zero_range(inode, offset, len, mode);
 
-	/*
-	 * Round up offset. This is not fallocate, we need to zero out
-	 * blocks, so convert interior block aligned part of the range to
-	 * unwritten and possibly manually zero out unaligned parts of the
-	 * range. Here, start and partial_begin are inclusive, end and
-	 * partial_end are exclusive.
-	 */
-	start = round_up(offset, 1 << blkbits);
-	end = round_down((offset + len), 1 << blkbits);
-
-	if (start < offset || end > offset + len)
-		return -EINVAL;
-	partial_begin = offset & ((1 << blkbits) - 1);
-	partial_end = (offset + len) & ((1 << blkbits) - 1);
-
-	lblk = start >> blkbits;
-	max_blocks = (end >> blkbits);
-	if (max_blocks < lblk)
-		max_blocks = 0;
-	else
-		max_blocks -= lblk;
-
 	inode_lock(inode);
 
 	/*
@@ -4581,26 +4556,23 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	 */
 	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
 		ret = -EOPNOTSUPP;
-		goto out_mutex;
+		goto out;
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-	    (offset + len > inode->i_size ||
-	     offset + len > EXT4_I(inode)->i_disksize)) {
-		new_size = offset + len;
+	    (end > inode->i_size || end > EXT4_I(inode)->i_disksize)) {
+		new_size = end;
 		ret = inode_newsize_ok(inode, new_size);
 		if (ret)
-			goto out_mutex;
+			goto out;
 	}
 
-	flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
-
 	/* Wait all existing dio workers, newcomers will block on i_rwsem */
 	inode_dio_wait(inode);
 
 	ret = file_modified(file);
 	if (ret)
-		goto out_mutex;
+		goto out;
 
 	/*
 	 * Prevent page faults from reinstantiating pages we have released
@@ -4616,36 +4588,40 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	 * Write data that will be zeroed to preserve them when successfully
 	 * discarding page cache below but fail to convert extents.
 	 */
-	ret = filemap_write_and_wait_range(mapping, start, end - 1);
+	ret = filemap_write_and_wait_range(mapping, offset, end - 1);
 	if (ret)
 		goto out_invalidate_lock;
 
+	/* Now release the pages and zero block aligned part of pages */
+	truncate_pagecache_range(inode, offset, end - 1);
+
+	flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
 	/* Preallocate the range including the unaligned edges */
-	if (partial_begin || partial_end) {
-		ret = ext4_alloc_file_blocks(file,
-				round_down(offset, 1 << blkbits) >> blkbits,
-				(round_up((offset + len), 1 << blkbits) -
-				 round_down(offset, 1 << blkbits)) >> blkbits,
-				new_size, flags);
+	if (offset & (blocksize - 1) || end & (blocksize - 1)) {
+		ext4_lblk_t alloc_lblk = offset >> blkbits;
+		ext4_lblk_t len_lblk = EXT4_MAX_BLOCKS(len, offset, blkbits);
+
+		ret = ext4_alloc_file_blocks(file, alloc_lblk, len_lblk,
+					     new_size, flags);
 		if (ret)
 			goto out_invalidate_lock;
 
 	}
 
 	/* Zero range excluding the unaligned edges */
-	if (max_blocks > 0) {
-		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
-			  EXT4_EX_NOCACHE);
-
-		/* Now release the pages and zero block aligned part of pages */
-		truncate_pagecache_range(inode, start, end - 1);
-
-		ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
-					     flags);
+	start_lblk = round_up(offset, blocksize) >> blkbits;
+	end_lblk = end >> blkbits;
+	if (end_lblk > start_lblk) {
+		ext4_lblk_t zero_blks = end_lblk - start_lblk;
+
+		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | EXT4_EX_NOCACHE);
+		ret = ext4_alloc_file_blocks(file, start_lblk, zero_blks,
+					     new_size, flags);
 		if (ret)
 			goto out_invalidate_lock;
 	}
-	if (!partial_begin && !partial_end)
+	/* Finish zeroing out if it doesn't contain partial block */
+	if (!(offset & (blocksize - 1)) && !(end & (blocksize - 1)))
 		goto out_invalidate_lock;
 
 	/*
@@ -4662,16 +4638,18 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 		goto out_invalidate_lock;
 	}
 
+	/* Zero out partial block at the edges of the range */
+	ret = ext4_zero_partial_blocks(handle, inode, offset, len);
+	if (ret)
+		goto out_handle;
+
 	if (new_size)
 		ext4_update_inode_size(inode, new_size);
 	ret = ext4_mark_inode_dirty(handle, inode);
 	if (unlikely(ret))
 		goto out_handle;
-	/* Zero out partial block at the edges of the range */
-	ret = ext4_zero_partial_blocks(handle, inode, offset, len);
-	if (ret >= 0)
-		ext4_update_inode_fsync_trans(handle, inode, 1);
 
+	ext4_update_inode_fsync_trans(handle, inode, 1);
 	if (file->f_flags & O_SYNC)
 		ext4_handle_sync(handle);
 
@@ -4679,7 +4657,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	ext4_journal_stop(handle);
 out_invalidate_lock:
 	filemap_invalidate_unlock(mapping);
-out_mutex:
+out:
 	inode_unlock(inode);
 	return ret;
 }
-- 
2.39.2