NTFS: Fix read regression.

The regression was caused by:
        commit[a32ea1e1f925399e0d81ca3f7394a44a6dafa12c] Fix read/truncate race

This causes ntfs_readpage() to be called for a zero i_size inode, which
failed when the file was compressed and non-resident.

Thanks a lot to Mike Galbraith for reporting the issue and tracking down
the commit that caused the regression.

Looking into it I found three bugs which the patch fixes.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
Tested-by:  Mike Galbraith <efault@gmx.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index cfdc7900d271..ad87cb01299b 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -405,6 +405,15 @@ static int ntfs_readpage(struct file *file, struct page *page)
 
 retry_readpage:
         BUG_ON(!PageLocked(page));
+        vi = page->mapping->host;
+        i_size = i_size_read(vi);
+        /* Is the page fully outside i_size? (truncate in progress) */
+        if (unlikely(page->index >= (i_size + PAGE_CACHE_SIZE - 1) >>
+                        PAGE_CACHE_SHIFT)) {
+                zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
+                ntfs_debug("Read outside i_size - truncated?");
+                goto done;
+        }
         /*
          * This can potentially happen because we clear PageUptodate() during
          * ntfs_writepage() of MstProtected() attributes.
@@ -413,7 +422,6 @@ retry_readpage:
                 unlock_page(page);
                 return 0;
         }
-        vi = page->mapping->host;
         ni = NTFS_I(vi);
         /*
          * Only $DATA attributes can be encrypted and only unnamed $DATA