[PATCH] fat: support a truncate() for expanding size (generic_cont_expand)
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>
diff --git a/fs/buffer.c b/fs/buffer.c
index 5287be1..5502323 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2160,11 +2160,12 @@
* 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 @@
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 @@
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(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);
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 15229fe..9b07c32 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -11,6 +11,7 @@
#include <linux/msdos_fs.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
+#include <linux/writeback.h>
int fat_generic_ioctl(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
@@ -124,6 +125,24 @@
.sendfile = generic_file_sendfile,
};
+static int fat_cont_expand(struct inode *inode, loff_t size)
+{
+ struct address_space *mapping = inode->i_mapping;
+ loff_t start = inode->i_size, count = size - inode->i_size;
+ int err;
+
+ err = generic_cont_expand_simple(inode, size);
+ if (err)
+ goto out;
+
+ inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
+ mark_inode_dirty(inode);
+ if (IS_SYNC(inode))
+ err = sync_page_range_nolock(inode, mapping, start, count);
+out:
+ return err;
+}
+
int fat_notify_change(struct dentry *dentry, struct iattr *attr)
{
struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
@@ -132,11 +151,17 @@
lock_kernel();
- /* FAT cannot truncate to a longer file */
+ /*
+ * Expand the file. Since inode_setattr() updates ->i_size
+ * before calling the ->truncate(), but FAT needs to fill the
+ * hole before it.
+ */
if (attr->ia_valid & ATTR_SIZE) {
if (attr->ia_size > inode->i_size) {
- error = -EPERM;
- goto out;
+ error = fat_cont_expand(inode, attr->ia_size);
+ if (error || attr->ia_valid == ATTR_SIZE)
+ goto out;
+ attr->ia_valid &= ~ATTR_SIZE;
}
}