NTFS: Fixup the resident attribute resizing code in

      fs/ntfs/aops.c::ntfs_{prepare,commit}_write()() and re-enable it.
      It should be safe now.  (Famous last words...)

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

2 files changed, 19 insertions, 7 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index 051c6818aad8..8a249df2b5c2 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -51,6 +51,11 @@ ToDo/Notes:
           value afterwards when reading the size of the bitmap inode.
         - Use i_size_{read,write}() in fs/ntfs/{aops.c,mft.c} and protect
           access to the i_size and other size fields using the size_lock.
+        - Implement extension of resident files in the regular file write code
+          paths (fs/ntfs/aops.c::ntfs_{prepare,commit}_write()).  At present
+          this only works until the data attribute becomes too big for the mft
+          record after which we abort the write returning -EOPNOTSUPP from
+          ntfs_prepare_write().
 
 2.1.22 - Many bug and race fixes and error handling improvements.
 
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index ac65806ee515..92215228eeab 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -872,6 +872,7 @@ static int ntfs_write_mst_block(struct page *page,
                 if (likely(block < rec_block)) {
                         if (unlikely(block >= dblock)) {
                                 clear_buffer_dirty(bh);
+                                set_buffer_uptodate(bh);
                                 continue;
                         }
                         /*
@@ -1830,6 +1831,7 @@ static int ntfs_prepare_write(struct file *file, struct page *page,
                 unsigned from, unsigned to)
 {
         s64 new_size;
+        unsigned long flags;
         struct inode *vi = page->mapping->host;
         ntfs_inode *base_ni = NULL, *ni = NTFS_I(vi);
         ntfs_volume *vol = ni->vol;
@@ -1903,12 +1905,6 @@ static int ntfs_prepare_write(struct file *file, struct page *page,
         /* If we do not need to resize the attribute allocation we are done. */
         if (new_size <= i_size_read(vi))
                 goto done;
-
-        // FIXME: We abort for now as this code is not safe.
-        ntfs_error(vi->i_sb, "Changing the file size is not supported yet.  "
-                        "Sorry.");
-        return -EOPNOTSUPP;
-
         /* Map, pin, and lock the (base) mft record. */
         if (!NInoAttr(ni))
                 base_ni = ni;
@@ -1937,7 +1933,17 @@ static int ntfs_prepare_write(struct file *file, struct page *page,
         a = ctx->attr;
         /* The total length of the attribute value. */
         attr_len = le32_to_cpu(a->data.resident.value_length);
-        BUG_ON(i_size_read(vi) != attr_len);
+        /* Fix an eventual previous failure of ntfs_commit_write(). */
+        read_lock_irqsave(&ni->size_lock, flags);
+        if (unlikely(ni->initialized_size < attr_len)) {
+                attr_len = ni->initialized_size;
+                a->data.resident.value_length = cpu_to_le32(attr_len);
+                BUG_ON(attr_len < i_size_read(vi));
+        }
+        read_unlock_irqrestore(&ni->size_lock, flags);
+        /* If we do not need to resize the attribute allocation we are done. */
+        if (new_size <= attr_len)
+                goto done_unm;
         /* Check if new size is allowed in $AttrDef. */
         err = ntfs_attr_size_bounds_check(vol, ni->type, new_size);
         if (unlikely(err)) {
@@ -1995,6 +2001,7 @@ static int ntfs_prepare_write(struct file *file, struct page *page,
         }
         flush_dcache_mft_record_page(ctx->ntfs_ino);
         mark_mft_record_dirty(ctx->ntfs_ino);
+done_unm:
         ntfs_attr_put_search_ctx(ctx);
         unmap_mft_record(base_ni);
         /*