Patchwork ext4: Only zero partial blocks in ext4_zero_partial_blocks()

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Submitter Lukas Czerner
Date June 20, 2013, 9:14 a.m.
Message ID <1371719673-3033-1-git-send-email-lczerner@redhat.com>
Download mbox | patch
Permalink /patch/252827/
State Accepted
Headers show

Comments

Lukas Czerner - June 20, 2013, 9:14 a.m.
Currently if we pass range into ext4_zero_partial_blocks() which covers
entire block we would attempt to zero it even though we should only zero
unaligned part of the block.

Fix this by checking whether the range covers the whole block skip
zeroing if so.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/inode.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)
Theodore Ts'o - June 20, 2013, 3:01 p.m.
On Thu, Jun 20, 2013 at 11:14:33AM +0200, Lukas Czerner wrote:
> Currently if we pass range into ext4_zero_partial_blocks() which covers
> entire block we would attempt to zero it even though we should only zero
> unaligned part of the block.
> 
> Fix this by checking whether the range covers the whole block skip
> zeroing if so.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>

Applied, thanks.

						- Ted
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Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3acf353..ce9f926 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3698,33 +3698,36 @@  int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
 {
 	struct super_block *sb = inode->i_sb;
 	struct address_space *mapping = inode->i_mapping;
-	unsigned partial = lstart & (sb->s_blocksize - 1);
+	unsigned partial_start, partial_end;
 	ext4_fsblk_t start, end;
 	loff_t byte_end = (lstart + length - 1);
 	int err = 0;
 
+	partial_start = lstart & (sb->s_blocksize - 1);
+	partial_end = byte_end & (sb->s_blocksize - 1);
+
 	start = lstart >> sb->s_blocksize_bits;
 	end = byte_end >> sb->s_blocksize_bits;
 
 	/* Handle partial zero within the single block */
-	if (start == end) {
+	if (start == end &&
+	    (partial_start || (partial_end != sb->s_blocksize - 1))) {
 		err = ext4_block_zero_page_range(handle, mapping,
 						 lstart, length);
 		return err;
 	}
 	/* Handle partial zero out on the start of the range */
-	if (partial) {
+	if (partial_start) {
 		err = ext4_block_zero_page_range(handle, mapping,
 						 lstart, sb->s_blocksize);
 		if (err)
 			return err;
 	}
 	/* Handle partial zero out on the end of the range */
-	partial = byte_end & (sb->s_blocksize - 1);
-	if (partial != sb->s_blocksize - 1)
+	if (partial_end != sb->s_blocksize - 1)
 		err = ext4_block_zero_page_range(handle, mapping,
-						 byte_end - partial,
-						 partial + 1);
+						 byte_end - partial_end,
+						 partial_end + 1);
 	return err;
 }