fs: introduce write_begin, write_end, and perform_write aops
These are intended to replace prepare_write and commit_write with more
flexible alternatives that are also able to avoid the buffered write
deadlock problems efficiently (which prepare_write is unable to do).
[mark.fasheh@oracle.com: API design contributions, code review and fixes]
[akpm@linux-foundation.org: various fixes]
[dmonakhov@sw.ru: new aop block_write_begin fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b9233a0..a5f993a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -204,14 +204,13 @@
* do_lo_send_aops - helper for writing data to a loop device
*
* This is the fast version for backing filesystems which implement the address
- * space operations prepare_write and commit_write.
+ * space operations write_begin and write_end.
*/
static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
- int bsize, loff_t pos, struct page *page)
+ int bsize, loff_t pos, struct page *unused)
{
struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
struct address_space *mapping = file->f_mapping;
- const struct address_space_operations *aops = mapping->a_ops;
pgoff_t index;
unsigned offset, bv_offs;
int len, ret;
@@ -223,63 +222,47 @@
len = bvec->bv_len;
while (len > 0) {
sector_t IV;
- unsigned size;
+ unsigned size, copied;
int transfer_result;
+ struct page *page;
+ void *fsdata;
IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
size = PAGE_CACHE_SIZE - offset;
if (size > len)
size = len;
- page = grab_cache_page(mapping, index);
- if (unlikely(!page))
+
+ ret = pagecache_write_begin(file, mapping, pos, size, 0,
+ &page, &fsdata);
+ if (ret)
goto fail;
- ret = aops->prepare_write(file, page, offset,
- offset + size);
- if (unlikely(ret)) {
- if (ret == AOP_TRUNCATED_PAGE) {
- page_cache_release(page);
- continue;
- }
- goto unlock;
- }
+
transfer_result = lo_do_transfer(lo, WRITE, page, offset,
bvec->bv_page, bv_offs, size, IV);
- if (unlikely(transfer_result)) {
- /*
- * The transfer failed, but we still write the data to
- * keep prepare/commit calls balanced.
- */
- printk(KERN_ERR "loop: transfer error block %llu\n",
- (unsigned long long)index);
- zero_user_page(page, offset, size, KM_USER0);
- }
- flush_dcache_page(page);
- ret = aops->commit_write(file, page, offset,
- offset + size);
- if (unlikely(ret)) {
- if (ret == AOP_TRUNCATED_PAGE) {
- page_cache_release(page);
- continue;
- }
- goto unlock;
- }
+ copied = size;
if (unlikely(transfer_result))
- goto unlock;
- bv_offs += size;
- len -= size;
+ copied = 0;
+
+ ret = pagecache_write_end(file, mapping, pos, size, copied,
+ page, fsdata);
+ if (ret < 0)
+ goto fail;
+ if (ret < copied)
+ copied = ret;
+
+ if (unlikely(transfer_result))
+ goto fail;
+
+ bv_offs += copied;
+ len -= copied;
offset = 0;
index++;
- pos += size;
- unlock_page(page);
- page_cache_release(page);
+ pos += copied;
}
ret = 0;
out:
mutex_unlock(&mapping->host->i_mutex);
return ret;
-unlock:
- unlock_page(page);
- page_cache_release(page);
fail:
ret = -1;
goto out;
@@ -313,7 +296,7 @@
* do_lo_send_direct_write - helper for writing data to a loop device
*
* This is the fast, non-transforming version for backing filesystems which do
- * not implement the address space operations prepare_write and commit_write.
+ * not implement the address space operations write_begin and write_end.
* It uses the write file operation which should be present on all writeable
* filesystems.
*/
@@ -332,7 +315,7 @@
* do_lo_send_write - helper for writing data to a loop device
*
* This is the slow, transforming version for filesystems which do not
- * implement the address space operations prepare_write and commit_write. It
+ * implement the address space operations write_begin and write_end. It
* uses the write file operation which should be present on all writeable
* filesystems.
*
@@ -780,7 +763,7 @@
*/
if (!file->f_op->splice_read)
goto out_putf;
- if (aops->prepare_write && aops->commit_write)
+ if (aops->prepare_write || aops->write_begin)
lo_flags |= LO_FLAGS_USE_AOPS;
if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
lo_flags |= LO_FLAGS_READ_ONLY;