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[PATCH] fat: support a truncate() for expanding size (generic_cont_expand)

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This patch changes generic_cont_expand(), in order to share the code
with fatfs.

  - Use vmtruncate() if ->prepare_write() returns a error.

Even if ->prepare_write() returns an error, it may already have added some
blocks.  So, this truncates blocks outside of ->i_size by vmtruncate().

  - Add generic_cont_expand_simple().

The generic_cont_expand_simple() assumes that ->prepare_write() can handle
the block boundary.  With this, we don't need to care the extra byte.

And for expanding a file size by truncate(), fatfs uses the
added generic_cont_expand_simple().

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
OGAWA Hirofumi
2006-01-08 01:02:13 -08:00
committed by Linus Torvalds
parent 268fc16e34
commit 05eb0b51fb
3 changed files with 76 additions and 18 deletions
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60
fs/buffer.c
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@ -2160,11 +2160,12 @@ int block_read_full_page(struct page *page, get_block_t *get_block)
* truncates. Uses prepare/commit_write to allow the filesystem to
* deal with the hole.
*/
int generic_cont_expand(struct inode *inode, loff_t size)
static int __generic_cont_expand(struct inode *inode, loff_t size,
pgoff_t index, unsigned int offset)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
unsigned long index, offset, limit;
unsigned long limit;
int err;
err = -EFBIG;
@ -2176,24 +2177,24 @@ int generic_cont_expand(struct inode *inode, loff_t size)
if (size > inode->i_sb->s_maxbytes)
goto out;
offset = (size & (PAGE_CACHE_SIZE-1)); /* Within page */
/* ugh. in prepare/commit_write, if from==to==start of block, we
** skip the prepare. make sure we never send an offset for the start
** of a block
*/
if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
offset++;
}
index = size >> PAGE_CACHE_SHIFT;
err = -ENOMEM;
page = grab_cache_page(mapping, index);
if (!page)
goto out;
err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
if (!err) {
err = mapping->a_ops->commit_write(NULL, page, offset, offset);
if (err) {
/*
* ->prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again.
*/
unlock_page(page);
page_cache_release(page);
vmtruncate(inode, inode->i_size);
goto out;
}
err = mapping->a_ops->commit_write(NULL, page, offset, offset);
unlock_page(page);
page_cache_release(page);
if (err > 0)
@ -2202,6 +2203,36 @@ out:
return err;
}
int generic_cont_expand(struct inode *inode, loff_t size)
{
pgoff_t index;
unsigned int offset;
offset = (size & (PAGE_CACHE_SIZE - 1)); /* Within page */
/* ugh. in prepare/commit_write, if from==to==start of block, we
** skip the prepare. make sure we never send an offset for the start
** of a block
*/
if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
/* caller must handle this extra byte. */
offset++;
}
index = size >> PAGE_CACHE_SHIFT;
return __generic_cont_expand(inode, size, index, offset);
}
int generic_cont_expand_simple(struct inode *inode, loff_t size)
{
loff_t pos = size - 1;
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
unsigned int offset = (pos & (PAGE_CACHE_SIZE - 1)) + 1;
/* prepare/commit_write can handle even if from==to==start of block. */
return __generic_cont_expand(inode, size, index, offset);
}
/*
* For moronic filesystems that do not allow holes in file.
* We may have to extend the file.
@ -3145,6 +3176,7 @@ EXPORT_SYMBOL(fsync_bdev);
EXPORT_SYMBOL(generic_block_bmap);
EXPORT_SYMBOL(generic_commit_write);
EXPORT_SYMBOL(generic_cont_expand);
EXPORT_SYMBOL(generic_cont_expand_simple);
EXPORT_SYMBOL(init_buffer);
EXPORT_SYMBOL(invalidate_bdev);
EXPORT_SYMBOL(ll_rw_block);