ext4: add new function ext4_block_zero_page_range()

This patch modifies the existing ext4_block_truncate_page() function
which was used by the truncate code path, and which zeroes out block
unaligned data, by adding a new length parameter, and renames it to
ext4_block_zero_page_rage().  This function can now be used to zero out the
head of a block, the tail of a block, or the middle
of a block.

The ext4_block_truncate_page() function is now a wrapper to
ext4_block_zero_page_range().

[ext4 punch hole patch series 2/5 v7]

Signed-off-by: Allison Henderson <achender@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Mingming Cao <cmm@us.ibm.com>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 2f310d1..c48f9db 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1825,6 +1825,8 @@ extern int ext4_writepage_trans_blocks(struct inode *);
 extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
 extern int ext4_block_truncate_page(handle_t *handle,
                struct address_space *mapping, loff_t from);
+extern int ext4_block_zero_page_range(handle_t *handle,
+               struct address_space *mapping, loff_t from, loff_t length);
 extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
 extern qsize_t *ext4_get_reserved_space(struct inode *inode);
 extern void ext4_da_update_reserve_space(struct inode *inode,

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index aef864b..fbe11e6 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3913,10 +3913,31 @@ void ext4_set_aops(struct inode *inode)
  */
 int ext4_block_truncate_page(handle_t *handle,
                struct address_space *mapping, loff_t from)
+{
+       unsigned offset = from & (PAGE_CACHE_SIZE-1);
+       unsigned length;
+       unsigned blocksize;
+       struct inode *inode = mapping->host;
+
+       blocksize = inode->i_sb->s_blocksize;
+       length = blocksize - (offset & (blocksize - 1));
+
+       return ext4_block_zero_page_range(handle, mapping, from, length);
+}
+
+/*
+ * ext4_block_zero_page_range() zeros out a mapping of length 'length'
+ * starting from file offset 'from'.  The range to be zero'd must
+ * be contained with in one block.  If the specified range exceeds
+ * the end of the block it will be shortened to end of the block
+ * that cooresponds to 'from'
+ */
+int ext4_block_zero_page_range(handle_t *handle,
+               struct address_space *mapping, loff_t from, loff_t length)
 {
        ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
-       unsigned blocksize, length, pos;
+       unsigned blocksize, max, pos;
        ext4_lblk_t iblock;
        struct inode *inode = mapping->host;
        struct buffer_head *bh;
@@ -3929,7 +3950,15 @@ int ext4_block_truncate_page(handle_t *handle,
                return -EINVAL;
 
        blocksize = inode->i_sb->s_blocksize;
-       length = blocksize - (offset & (blocksize - 1));
+       max = blocksize - (offset & (blocksize - 1));
+
+       /*
+        * correct length if it does not fall between
+        * 'from' and the end of the block
+        */
+       if (length > max || length < 0)
+               length = max;
+
        iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
 
        if (!page_has_buffers(page))