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>

1 files changed, 11 insertions, 35 deletions

diff --git a/fs/namei.c b/fs/namei.c
index a83160acd748..b40b8084eefc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2729,53 +2729,29 @@ int __page_symlink(struct inode *inode, const char *symname, int len,
 {
         struct address_space *mapping = inode->i_mapping;
         struct page *page;
+        void *fsdata;
         int err;
         char *kaddr;
 
 retry:
-        err = -ENOMEM;
-        page = find_or_create_page(mapping, 0, gfp_mask);
-        if (!page)
-                goto fail;
-        err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
-        if (err == AOP_TRUNCATED_PAGE) {
-                page_cache_release(page);
-                goto retry;
-        }
+        err = pagecache_write_begin(NULL, mapping, 0, len-1,
+                                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
         if (err)
-                goto fail_map;
+                goto fail;
+
         kaddr = kmap_atomic(page, KM_USER0);
         memcpy(kaddr, symname, len-1);
         kunmap_atomic(kaddr, KM_USER0);
-        err = mapping->a_ops->commit_write(NULL, page, 0, len-1);
-        if (err == AOP_TRUNCATED_PAGE) {
-                page_cache_release(page);
-                goto retry;
-        }
-        if (err)
-                goto fail_map;
-        /*
-         * Notice that we are _not_ going to block here - end of page is
-         * unmapped, so this will only try to map the rest of page, see
-         * that it is unmapped (typically even will not look into inode -
-         * ->i_size will be enough for everything) and zero it out.
-         * OTOH it's obviously correct and should make the page up-to-date.
-         */
-        if (!PageUptodate(page)) {
-                err = mapping->a_ops->readpage(NULL, page);
-                if (err != AOP_TRUNCATED_PAGE)
-                        wait_on_page_locked(page);
-        } else {
-                unlock_page(page);
-        }
-        page_cache_release(page);
+
+        err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
+                                                        page, fsdata);
         if (err < 0)
                 goto fail;
+        if (err < len-1)
+                goto retry;
+
         mark_inode_dirty(inode);
         return 0;
-fail_map:
-        unlock_page(page);
-        page_cache_release(page);
 fail:
         return err;
 }