REISER4: fix for reiser4_write_extent

[Ignatich <ignatich@gmail.com>]

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While trying to find the cause of problems with reiser4 in recent 
kernels I came across this.

Incomplete write handling seem to be missing from reiser4_write_extent() 
thanks to reiser4-temp-fix.patch. Strangely, there is a patch by Edward 
Shishkin that should address that issue, but it is missing from -mm 
tree. Please check.

    Max


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------------------------------------------------------
Subject: reiser4: fix write_extent
From: Edward Shishkin <[EMAIL PROTECTED]>

. Fix reiser4_write_extent():
   1) handling incomplete writes missed in reiser4-temp-fix.patch
   2) bugs in the case of returned errors


Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---

 fs/reiser4/plugin/item/extent_file_ops.c |   64 ++++++++++++---------
 1 file changed, 37 insertions(+), 27 deletions(-)

diff -puN fs/reiser4/plugin/item/extent_file_ops.c~reiser4-fix-write_extent 
fs/reiser4/plugin/item/extent_file_ops.c
--- a/fs/reiser4/plugin/item/extent_file_ops.c~reiser4-fix-write_extent
+++ a/fs/reiser4/plugin/item/extent_file_ops.c
@@ -941,15 +941,15 @@ static int write_extent_reserve_space(st
  * reiser4_write_extent - write method of extent item plugin
  * @file: file to write to
  * @buf: address of user-space buffer
- * @write_amount: number of bytes to write
- * @off: position in file to write to
+ * @count: number of bytes to write
+ * @pos: position in file to write to
  *
  */
 ssize_t reiser4_write_extent(struct file *file, const char __user *buf,
                             size_t count, loff_t *pos)
 {
        int have_to_update_extent;
-       int nr_pages;
+       int nr_pages, nr_dirty;
        struct page *page;
        jnode *jnodes[WRITE_GRANULARITY + 1];
        struct inode *inode;
@@ -958,7 +958,7 @@ ssize_t reiser4_write_extent(struct file
        int i;
        int to_page, page_off;
        size_t left, written;
-       int result;
+       int result = 0;
 
        inode = file->f_dentry->d_inode;
        if (write_extent_reserve_space(inode))
@@ -972,10 +972,12 @@ ssize_t reiser4_write_extent(struct file
 
        BUG_ON(get_current_context()->trans->atom != NULL);
 
+       left = count;
        index = *pos >> PAGE_CACHE_SHIFT;
        /* calculate number of pages which are to be written */
        end = ((*pos + count - 1) >> PAGE_CACHE_SHIFT);
        nr_pages = end - index + 1;
+       nr_dirty = 0;
        assert("", nr_pages <= WRITE_GRANULARITY + 1);
 
        /* get pages and jnodes */
@@ -983,22 +985,17 @@ ssize_t reiser4_write_extent(struct file
                page = find_or_create_page(inode->i_mapping, index + i,
                                           reiser4_ctx_gfp_mask_get());
                if (page == NULL) {
-                       while(i --) {
-                               unlock_page(jnode_page(jnodes[i]));
-                               page_cache_release(jnode_page(jnodes[i]));
-                       }
-                       return RETERR(-ENOMEM);
+                       nr_pages = i;
+                       result = RETERR(-ENOMEM);
+                       goto out;
                }
-
                jnodes[i] = jnode_of_page(page);
                if (IS_ERR(jnodes[i])) {
                        unlock_page(page);
                        page_cache_release(page);
-                       while (i --) {
-                               jput(jnodes[i]);
-                               page_cache_release(jnode_page(jnodes[i]));
-                       }
-                       return RETERR(-ENOMEM);
+                       nr_pages = i;
+                       result = RETERR(-ENOMEM);
+                       goto out;
                }
                /* prevent jnode and page from disconnecting */
                JF_SET(jnodes[i], JNODE_WRITE_PREPARED);
@@ -1009,7 +1006,6 @@ ssize_t reiser4_write_extent(struct file
 
        have_to_update_extent = 0;
 
-       left = count;
        page_off = (*pos & (PAGE_CACHE_SIZE - 1));
        for (i = 0; i < nr_pages; i ++) {
                to_page = PAGE_CACHE_SIZE - page_off;
@@ -1050,14 +1046,26 @@ ssize_t reiser4_write_extent(struct file
                        flush_dcache_page(page);
                        kunmap_atomic(kaddr, KM_USER0);
                }
-
-               written = filemap_copy_from_user(page, page_off, buf, to_page);
+               written = filemap_copy_from_user_atomic(page, page_off, buf,
+                                                       to_page);
+               if (written != to_page)
+                       /* Do it the slow way */
+                       written = filemap_copy_from_user_nonatomic(page,
+                                                                  page_off,
+                                                                  buf,
+                                                                  to_page);
+               if (unlikely(written != to_page)) {
+                       unlock_page(page);
+                       result = RETERR(-EFAULT);
+                       break;
+               }
                flush_dcache_page(page);
                reiser4_set_page_dirty_internal(page);
                unlock_page(page);
+               nr_dirty ++;
+
                mark_page_accessed(page);
                SetPageUptodate(page);
-               page_cache_release(page);
 
                if (jnodes[i]->blocknr == 0)
                        have_to_update_extent ++;
@@ -1067,27 +1075,29 @@ ssize_t reiser4_write_extent(struct file
                left -= to_page;
                BUG_ON(get_current_context()->trans->atom != NULL);
        }
-
        if (have_to_update_extent) {
-               update_extents(file, jnodes, nr_pages, *pos);
+               update_extents(file, jnodes, nr_dirty, *pos);
        } else {
-               for (i = 0; i < nr_pages; i ++) {
+               for (i = 0; i < nr_dirty; i ++) {
+                       int ret;
                        spin_lock_jnode(jnodes[i]);
-                       result = reiser4_try_capture(jnodes[i],
+                       ret = reiser4_try_capture(jnodes[i],
                                                     ZNODE_WRITE_LOCK, 0);
-                       BUG_ON(result != 0);
+                       BUG_ON(ret != 0);
                        jnode_make_dirty_locked(jnodes[i]);
                        spin_unlock_jnode(jnodes[i]);
                }
        }
-
+ out:
        for (i = 0; i < nr_pages; i ++) {
+               page_cache_release(jnode_page(jnodes[i]));
                JF_CLR(jnodes[i], JNODE_WRITE_PREPARED);
                jput(jnodes[i]);
        }
+       /* the only errors handled so far is ENOMEM and
+          EFAULT on copy_from_user  */
 
-       /* the only error handled so far is EFAULT on copy_from_user  */
-       return (count - left) ? (count - left) : -EFAULT;
+       return (count - left) ? (count - left) : result;
 }
 
 static inline void zero_page(struct page *page)