NTFS: - Modify ->readpage and ->writepage (fs/ntfs/aops.c) so they detect

        and handle the case where an attribute is converted from resident
        to non-resident by a concurrent file write.
      - Reorder some operations when converting an attribute from resident
        to non-resident (fs/ntfs/attrib.c) so it is safe wrt concurrent
        ->readpage and ->writepage.

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

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 2a7cba258cca..6241c4cfbe28 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -355,6 +355,7 @@ static int ntfs_readpage(struct file *file, struct page *page)
         u32 attr_len;
         int err = 0;
 
+retry_readpage:
         BUG_ON(!PageLocked(page));
         /*
          * This can potentially happen because we clear PageUptodate() during
@@ -408,6 +409,14 @@ static int ntfs_readpage(struct file *file, struct page *page)
                 err = PTR_ERR(mrec);
                 goto err_out;
         }
+        /*
+         * If a parallel write made the attribute non-resident, drop the mft
+         * record and retry the readpage.
+         */
+        if (unlikely(NInoNonResident(ni))) {
+                unmap_mft_record(base_ni);
+                goto retry_readpage;
+        }
         ctx = ntfs_attr_get_search_ctx(base_ni, mrec);
         if (unlikely(!ctx)) {
                 err = -ENOMEM;
@@ -1248,6 +1257,7 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
         u32 attr_len;
         int err;
 
+retry_writepage:
         BUG_ON(!PageLocked(page));
         i_size = i_size_read(vi);
         /* Is the page fully outside i_size? (truncate in progress) */
@@ -1338,6 +1348,14 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
                 ctx = NULL;
                 goto err_out;
         }
+        /*
+         * If a parallel write made the attribute non-resident, drop the mft
+         * record and retry the writepage.
+         */
+        if (unlikely(NInoNonResident(ni))) {
+                unmap_mft_record(base_ni);
+                goto retry_writepage;
+        }
         ctx = ntfs_attr_get_search_ctx(base_ni, m);
         if (unlikely(!ctx)) {
                 err = -ENOMEM;