fs: remove prepare_write/commit_write

Nothing uses prepare_write or commit_write. Remove them from the tree
completely.

[akpm@linux-foundation.org: schedule simple_prepare_write() for unexporting]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 238 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index ab8553658af3..f3e5f8944d17 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2029,48 +2029,8 @@ int pagecache_write_begin(struct file *file, struct address_space *mapping,
 {
         const struct address_space_operations *aops = mapping->a_ops;
 
-        if (aops->write_begin) {
-                return aops->write_begin(file, mapping, pos, len, flags,
+        return aops->write_begin(file, mapping, pos, len, flags,
                                                         pagep, fsdata);
-        } else {
-                int ret;
-                pgoff_t index = pos >> PAGE_CACHE_SHIFT;
-                unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
-                struct inode *inode = mapping->host;
-                struct page *page;
-again:
-                page = __grab_cache_page(mapping, index);
-                *pagep = page;
-                if (!page)
-                        return -ENOMEM;
-
-                if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
-                        /*
-                         * There is no way to resolve a short write situation
-                         * for a !Uptodate page (except by double copying in
-                         * the caller done by generic_perform_write_2copy).
-                         *
-                         * Instead, we have to bring it uptodate here.
-                         */
-                        ret = aops->readpage(file, page);
-                        page_cache_release(page);
-                        if (ret) {
-                                if (ret == AOP_TRUNCATED_PAGE)
-                                        goto again;
-                                return ret;
-                        }
-                        goto again;
-                }
-
-                ret = aops->prepare_write(file, page, offset, offset+len);
-                if (ret) {
-                        unlock_page(page);
-                        page_cache_release(page);
-                        if (pos + len > inode->i_size)
-                                vmtruncate(inode, inode->i_size);
-                }
-                return ret;
-        }
 }
 EXPORT_SYMBOL(pagecache_write_begin);
 
@@ -2079,32 +2039,9 @@ int pagecache_write_end(struct file *file, struct address_space *mapping,
                                 struct page *page, void *fsdata)
 {
         const struct address_space_operations *aops = mapping->a_ops;
-        int ret;
-
-        if (aops->write_end) {
-                mark_page_accessed(page);
-                ret = aops->write_end(file, mapping, pos, len, copied,
-                                                        page, fsdata);
-        } else {
-                unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
-                struct inode *inode = mapping->host;
-
-                flush_dcache_page(page);
-                ret = aops->commit_write(file, page, offset, offset+len);
-                unlock_page(page);
-                mark_page_accessed(page);
-                page_cache_release(page);
-
-                if (ret < 0) {
-                        if (pos + len > inode->i_size)
-                                vmtruncate(inode, inode->i_size);
-                } else if (ret > 0)
-                        ret = min_t(size_t, copied, ret);
-                else
-                        ret = copied;
-        }
 
-        return ret;
+        mark_page_accessed(page);
+        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
 }
 EXPORT_SYMBOL(pagecache_write_end);
 
@@ -2226,174 +2163,6 @@ repeat:
 }
 EXPORT_SYMBOL(__grab_cache_page);
 
-static ssize_t generic_perform_write_2copy(struct file *file,
-                                struct iov_iter *i, loff_t pos)
-{
-        struct address_space *mapping = file->f_mapping;
-        const struct address_space_operations *a_ops = mapping->a_ops;
-        struct inode *inode = mapping->host;
-        long status = 0;
-        ssize_t written = 0;
-
-        do {
-                struct page *src_page;
-                struct page *page;
-                pgoff_t index;          /* Pagecache index for current page */
-                unsigned long offset;   /* Offset into pagecache page */
-                unsigned long bytes;    /* Bytes to write to page */
-                size_t copied;          /* Bytes copied from user */
-
-                offset = (pos & (PAGE_CACHE_SIZE - 1));
-                index = pos >> PAGE_CACHE_SHIFT;
-                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
-                                                iov_iter_count(i));
-
-                /*
-                 * a non-NULL src_page indicates that we're doing the
-                 * copy via get_user_pages and kmap.
-                 */
-                src_page = NULL;
-
-                /*
-                 * Bring in the user page that we will copy from _first_.
-                 * Otherwise there's a nasty deadlock on copying from the
-                 * same page as we're writing to, without it being marked
-                 * up-to-date.
-                 *
-                 * Not only is this an optimisation, but it is also required
-                 * to check that the address is actually valid, when atomic
-                 * usercopies are used, below.
-                 */
-                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
-                        status = -EFAULT;
-                        break;
-                }
-
-                page = __grab_cache_page(mapping, index);
-                if (!page) {
-                        status = -ENOMEM;
-                        break;
-                }
-
-                /*
-                 * non-uptodate pages cannot cope with short copies, and we
-                 * cannot take a pagefault with the destination page locked.
-                 * So pin the source page to copy it.
-                 */
-                if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) {
-                        unlock_page(page);
-
-                        src_page = alloc_page(GFP_KERNEL);
-                        if (!src_page) {
-                                page_cache_release(page);
-                                status = -ENOMEM;
-                                break;
-                        }
-
-                        /*
-                         * Cannot get_user_pages with a page locked for the
-                         * same reason as we can't take a page fault with a
-                         * page locked (as explained below).
-                         */
-                        copied = iov_iter_copy_from_user(src_page, i,
-                                                                offset, bytes);
-                        if (unlikely(copied == 0)) {
-                                status = -EFAULT;
-                                page_cache_release(page);
-                                page_cache_release(src_page);
-                                break;
-                        }
-                        bytes = copied;
-
-                        lock_page(page);
-                        /*
-                         * Can't handle the page going uptodate here, because
-                         * that means we would use non-atomic usercopies, which
-                         * zero out the tail of the page, which can cause
-                         * zeroes to become transiently visible. We could just
-                         * use a non-zeroing copy, but the APIs aren't too
-                         * consistent.
-                         */
-                        if (unlikely(!page->mapping || PageUptodate(page))) {
-                                unlock_page(page);
-                                page_cache_release(page);
-                                page_cache_release(src_page);
-                                continue;
-                        }
-                }
-
-                status = a_ops->prepare_write(file, page, offset, offset+bytes);
-                if (unlikely(status))
-                        goto fs_write_aop_error;
-
-                if (!src_page) {
-                        /*
-                         * Must not enter the pagefault handler here, because
-                         * we hold the page lock, so we might recursively
-                         * deadlock on the same lock, or get an ABBA deadlock
-                         * against a different lock, or against the mmap_sem
-                         * (which nests outside the page lock).  So increment
-                         * preempt count, and use _atomic usercopies.
-                         *
-                         * The page is uptodate so we are OK to encounter a
-                         * short copy: if unmodified parts of the page are
-                         * marked dirty and written out to disk, it doesn't
-                         * really matter.
-                         */
-                        pagefault_disable();
-                        copied = iov_iter_copy_from_user_atomic(page, i,
-                                                                offset, bytes);
-                        pagefault_enable();
-                } else {
-                        void *src, *dst;
-                        src = kmap_atomic(src_page, KM_USER0);
-                        dst = kmap_atomic(page, KM_USER1);
-                        memcpy(dst + offset, src + offset, bytes);
-                        kunmap_atomic(dst, KM_USER1);
-                        kunmap_atomic(src, KM_USER0);
-                        copied = bytes;
-                }
-                flush_dcache_page(page);
-
-                status = a_ops->commit_write(file, page, offset, offset+bytes);
-                if (unlikely(status < 0))
-                        goto fs_write_aop_error;
-                if (unlikely(status > 0)) /* filesystem did partial write */
-                        copied = min_t(size_t, copied, status);
-
-                unlock_page(page);
-                mark_page_accessed(page);
-                page_cache_release(page);
-                if (src_page)
-                        page_cache_release(src_page);
-
-                iov_iter_advance(i, copied);
-                pos += copied;
-                written += copied;
-
-                balance_dirty_pages_ratelimited(mapping);
-                cond_resched();
-                continue;
-
-fs_write_aop_error:
-                unlock_page(page);
-                page_cache_release(page);
-                if (src_page)
-                        page_cache_release(src_page);
-
-                /*
-                 * prepare_write() may have instantiated a few blocks
-                 * outside i_size.  Trim these off again. Don't need
-                 * i_size_read because we hold i_mutex.
-                 */
-                if (pos + bytes > inode->i_size)
-                        vmtruncate(inode, inode->i_size);
-                break;
-        } while (iov_iter_count(i));
-
-        return written ? written : status;
-}
-
 static ssize_t generic_perform_write(struct file *file,
                                 struct iov_iter *i, loff_t pos)
 {
@@ -2494,10 +2263,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
         struct iov_iter i;
 
         iov_iter_init(&i, iov, nr_segs, count, written);
-        if (a_ops->write_begin)
-                status = generic_perform_write(file, &i, pos);
-        else
-                status = generic_perform_write_2copy(file, &i, pos);
+        status = generic_perform_write(file, &i, pos);
 
         if (likely(status >= 0)) {
                 written += status;