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, 10 insertions, 0 deletions

diff --git a/fs/ntfs/compress.c b/fs/ntfs/compress.c
index d98daf59e0b6..d1619d05eb23 100644
--- a/fs/ntfs/compress.c
+++ b/fs/ntfs/compress.c
@@ -561,6 +561,16 @@ int ntfs_read_compressed_block(struct page *page)
         read_unlock_irqrestore(&ni->size_lock, flags);
         max_page = ((i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
                         offset;
+        /* Is the page fully outside i_size? (truncate in progress) */
+        if (xpage >= max_page) {
+                kfree(bhs);
+                kfree(pages);
+                zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
+                ntfs_debug("Compressed read outside i_size - truncated?");
+                SetPageUptodate(page);
+                unlock_page(page);
+                return 0;
+        }
         if (nr_pages < max_page)
                 max_page = nr_pages;
         for (i = 0; i < max_page; i++, offset++) {