afs: convert to new aops

Cannot assume writes will fully complete, so this conversion goes the easy
way and always brings the page uptodate before the write.

[dhowells@redhat.com: style tweaks]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 51 insertions, 92 deletions

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 525f7c56e068..a3901769a96c 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -50,8 +50,8 @@ const struct address_space_operations afs_fs_aops = {
         .launder_page   = afs_launder_page,
         .releasepage    = afs_releasepage,
         .invalidatepage = afs_invalidatepage,
-        .prepare_write  = afs_prepare_write,
-        .commit_write   = afs_commit_write,
+        .write_begin    = afs_write_begin,
+        .write_end      = afs_write_end,
         .writepage      = afs_writepage,
         .writepages     = afs_writepages,
 };
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 3cb6920ff30b..67f259d99cd6 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -728,8 +728,12 @@ extern int afs_volume_release_fileserver(struct afs_vnode *,
  */
 extern int afs_set_page_dirty(struct page *);
 extern void afs_put_writeback(struct afs_writeback *);
-extern int afs_prepare_write(struct file *, struct page *, unsigned, unsigned);
-extern int afs_commit_write(struct file *, struct page *, unsigned, unsigned);
+extern int afs_write_begin(struct file *file, struct address_space *mapping,
+                        loff_t pos, unsigned len, unsigned flags,
+                        struct page **pagep, void **fsdata);
+extern int afs_write_end(struct file *file, struct address_space *mapping,
+                        loff_t pos, unsigned len, unsigned copied,
+                        struct page *page, void *fsdata);
 extern int afs_writepage(struct page *, struct writeback_control *);
 extern int afs_writepages(struct address_space *, struct writeback_control *);
 extern int afs_write_inode(struct inode *, int);
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 065b4e10681a..d6b85dab35fc 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -84,15 +84,23 @@ void afs_put_writeback(struct afs_writeback *wb)
  * partly or wholly fill a page that's under preparation for writing
  */
 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
-                         unsigned start, unsigned len, struct page *page)
+                         loff_t pos, unsigned len, struct page *page)
 {
+        loff_t i_size;
+        unsigned eof;
         int ret;
 
-        _enter(",,%u,%u", start, len);
+        _enter(",,%llu,%u", (unsigned long long)pos, len);
 
-        ASSERTCMP(start + len, <=, PAGE_SIZE);
+        ASSERTCMP(len, <=, PAGE_CACHE_SIZE);
 
-        ret = afs_vnode_fetch_data(vnode, key, start, len, page);
+        i_size = i_size_read(&vnode->vfs_inode);
+        if (pos + len > i_size)
+                eof = i_size;
+        else
+                eof = PAGE_CACHE_SIZE;
+
+        ret = afs_vnode_fetch_data(vnode, key, 0, eof, page);
         if (ret < 0) {
                 if (ret == -ENOENT) {
                         _debug("got NOENT from server"
@@ -107,109 +115,55 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 }
 
 /*
- * prepare a page for being written to
- */
-static int afs_prepare_page(struct afs_vnode *vnode, struct page *page,
-                            struct key *key, unsigned offset, unsigned to)
-{
-        unsigned eof, tail, start, stop, len;
-        loff_t i_size, pos;
-        void *p;
-        int ret;
-
-        _enter("");
-
-        if (offset == 0 && to == PAGE_SIZE)
-                return 0;
-
-        p = kmap_atomic(page, KM_USER0);
-
-        i_size = i_size_read(&vnode->vfs_inode);
-        pos = (loff_t) page->index << PAGE_SHIFT;
-        if (pos >= i_size) {
-                /* partial write, page beyond EOF */
-                _debug("beyond");
-                if (offset > 0)
-                        memset(p, 0, offset);
-                if (to < PAGE_SIZE)
-                        memset(p + to, 0, PAGE_SIZE - to);
-                kunmap_atomic(p, KM_USER0);
-                return 0;
-        }
-
-        if (i_size - pos >= PAGE_SIZE) {
-                /* partial write, page entirely before EOF */
-                _debug("before");
-                tail = eof = PAGE_SIZE;
-        } else {
-                /* partial write, page overlaps EOF */
-                eof = i_size - pos;
-                _debug("overlap %u", eof);
-                tail = max(eof, to);
-                if (tail < PAGE_SIZE)
-                        memset(p + tail, 0, PAGE_SIZE - tail);
-                if (offset > eof)
-                        memset(p + eof, 0, PAGE_SIZE - eof);
-        }
-
-        kunmap_atomic(p, KM_USER0);
-
-        ret = 0;
-        if (offset > 0 || eof > to) {
-                /* need to fill one or two bits that aren't going to be written
-                 * (cover both fillers in one read if there are two) */
-                start = (offset > 0) ? 0 : to;
-                stop = (eof > to) ? eof : offset;
-                len = stop - start;
-                _debug("wr=%u-%u av=0-%u rd=%u@%u",
-                       offset, to, eof, start, len);
-                ret = afs_fill_page(vnode, key, start, len, page);
-        }
-
-        _leave(" = %d", ret);
-        return ret;
-}
-
-/*
  * prepare to perform part of a write to a page
- * - the caller holds the page locked, preventing it from being written out or
- *   modified by anyone else
  */
-int afs_prepare_write(struct file *file, struct page *page,
-                      unsigned offset, unsigned to)
+int afs_write_begin(struct file *file, struct address_space *mapping,
+                    loff_t pos, unsigned len, unsigned flags,
+                    struct page **pagep, void **fsdata)
 {
         struct afs_writeback *candidate, *wb;
         struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
+        struct page *page;
         struct key *key = file->private_data;
-        pgoff_t index;
+        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+        unsigned to = from + len;
+        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
         int ret;
 
         _enter("{%x:%u},{%lx},%u,%u",
-               vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
+               vnode->fid.vid, vnode->fid.vnode, index, from, to);
 
         candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
         if (!candidate)
                 return -ENOMEM;
         candidate->vnode = vnode;
-        candidate->first = candidate->last = page->index;
-        candidate->offset_first = offset;
+        candidate->first = candidate->last = index;
+        candidate->offset_first = from;
         candidate->to_last = to;
         candidate->usage = 1;
         candidate->state = AFS_WBACK_PENDING;
         init_waitqueue_head(&candidate->waitq);
 
+        page = __grab_cache_page(mapping, index);
+        if (!page) {
+                kfree(candidate);
+                return -ENOMEM;
+        }
+        *pagep = page;
+        /* page won't leak in error case: it eventually gets cleaned off LRU */
+
         if (!PageUptodate(page)) {
                 _debug("not up to date");
-                ret = afs_prepare_page(vnode, page, key, offset, to);
+                ret = afs_fill_page(vnode, key, pos, len, page);
                 if (ret < 0) {
                         kfree(candidate);
                         _leave(" = %d [prep]", ret);
                         return ret;
                 }
+                SetPageUptodate(page);
         }
 
 try_again:
-        index = page->index;
         spin_lock(&vnode->writeback_lock);
 
         /* see if this page is already pending a writeback under a suitable key
@@ -242,8 +196,8 @@ try_again:
 subsume_in_current_wb:
         _debug("subsume");
         ASSERTRANGE(wb->first, <=, index, <=, wb->last);
-        if (index == wb->first && offset < wb->offset_first)
-                wb->offset_first = offset;
+        if (index == wb->first && from < wb->offset_first)
+                wb->offset_first = from;
         if (index == wb->last && to > wb->to_last)
                 wb->to_last = to;
         spin_unlock(&vnode->writeback_lock);
@@ -289,17 +243,17 @@ flush_conflicting_wb:
 /*
  * finalise part of a write to a page
  */
-int afs_commit_write(struct file *file, struct page *page,
-                     unsigned offset, unsigned to)
+int afs_write_end(struct file *file, struct address_space *mapping,
+                  loff_t pos, unsigned len, unsigned copied,
+                  struct page *page, void *fsdata)
 {
         struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
         loff_t i_size, maybe_i_size;
 
-        _enter("{%x:%u},{%lx},%u,%u",
-               vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
+        _enter("{%x:%u},{%lx}",
+               vnode->fid.vid, vnode->fid.vnode, page->index);
 
-        maybe_i_size = (loff_t) page->index << PAGE_SHIFT;
-        maybe_i_size += to;
+        maybe_i_size = pos + copied;
 
         i_size = i_size_read(&vnode->vfs_inode);
         if (maybe_i_size > i_size) {
@@ -310,12 +264,13 @@ int afs_commit_write(struct file *file, struct page *page,
                 spin_unlock(&vnode->writeback_lock);
         }
 
-        SetPageUptodate(page);
         set_page_dirty(page);
         if (PageDirty(page))
                 _debug("dirtied");
+        unlock_page(page);
+        page_cache_release(page);
 
-        return 0;
+        return copied;
 }
 
 /*