NTFS: Fixup handling of sparse, compressed, and encrypted attributes in

      fs/ntfs/aops.c::ntfs_writepage().

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

2 files changed, 49 insertions, 57 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index b1766642baf8..4b8666d7e7fe 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -79,6 +79,8 @@ ToDo/Notes:
           fs/ntfs/inode.c::ntfs_read_locked_{,attr_,index_}inode().
         - Make ntfs_write_block() not instantiate sparse blocks if they contain
           only zeroes.
+        - Fixup handling of sparse, compressed, and encrypted attributes in
+          fs/ntfs/aops.c::ntfs_writepage().
 
 2.1.23 - Implement extension of resident files and make writing safe as well as
          many bug fixes, cleanups, and enhancements...
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index f3ad36d8b8c9..6f2954aac5a2 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -1301,38 +1301,42 @@ retry_writepage:
                 ntfs_debug("Write outside i_size - truncated?");
                 return 0;
         }
+        /*
+         * Only $DATA attributes can be encrypted and only unnamed $DATA
+         * attributes can be compressed.  Index root can have the flags set but
+         * this means to create compressed/encrypted files, not that the
+         * attribute is compressed/encrypted.
+         */
+        if (ni->type != AT_INDEX_ROOT) {
+                /* If file is encrypted, deny access, just like NT4. */
+                if (NInoEncrypted(ni)) {
+                        unlock_page(page);
+                        BUG_ON(ni->type != AT_DATA);
+                        ntfs_debug("Denying write access to encrypted "
+                                        "file.");
+                        return -EACCES;
+                }
+                /* Compressed data streams are handled in compress.c. */
+                if (NInoNonResident(ni) && NInoCompressed(ni)) {
+                        BUG_ON(ni->type != AT_DATA);
+                        BUG_ON(ni->name_len);
+                        // TODO: Implement and replace this with
+                        // return ntfs_write_compressed_block(page);
+                        unlock_page(page);
+                        ntfs_error(vi->i_sb, "Writing to compressed files is "
+                                        "not supported yet.  Sorry.");
+                        return -EOPNOTSUPP;
+                }
+                // TODO: Implement and remove this check.
+                if (NInoNonResident(ni) && NInoSparse(ni)) {
+                        unlock_page(page);
+                        ntfs_error(vi->i_sb, "Writing to sparse files is not "
+                                        "supported yet.  Sorry.");
+                        return -EOPNOTSUPP;
+                }
+        }
         /* NInoNonResident() == NInoIndexAllocPresent() */
         if (NInoNonResident(ni)) {
-                /*
-                 * Only unnamed $DATA attributes can be compressed, encrypted,
-                 * and/or sparse.
-                 */
-                if (ni->type == AT_DATA && !ni->name_len) {
-                        /* If file is encrypted, deny access, just like NT4. */
-                        if (NInoEncrypted(ni)) {
-                                unlock_page(page);
-                                ntfs_debug("Denying write access to encrypted "
-                                                "file.");
-                                return -EACCES;
-                        }
-                        /* Compressed data streams are handled in compress.c. */
-                        if (NInoCompressed(ni)) {
-                                // TODO: Implement and replace this check with
-                                // return ntfs_write_compressed_block(page);
-                                unlock_page(page);
-                                ntfs_error(vi->i_sb, "Writing to compressed "
-                                                "files is not supported yet. "
-                                                "Sorry.");
-                                return -EOPNOTSUPP;
-                        }
-                        // TODO: Implement and remove this check.
-                        if (NInoSparse(ni)) {
-                                unlock_page(page);
-                                ntfs_error(vi->i_sb, "Writing to sparse files "
-                                                "is not supported yet. Sorry.");
-                                return -EOPNOTSUPP;
-                        }
-                }
                 /* We have to zero every time due to mmap-at-end-of-file. */
                 if (page->index >= (i_size >> PAGE_CACHE_SHIFT)) {
                         /* The page straddles i_size. */
@@ -1345,14 +1349,16 @@ retry_writepage:
                 /* Handle mst protected attributes. */
                 if (NInoMstProtected(ni))
                         return ntfs_write_mst_block(page, wbc);
-                /* Normal data stream. */
+                /* Normal, non-resident data stream. */
                 return ntfs_write_block(page, wbc);
         }
         /*
-         * Attribute is resident, implying it is not compressed, encrypted,
-         * sparse, or mst protected.  This also means the attribute is smaller
-         * than an mft record and hence smaller than a page, so can simply
-         * return error on any pages with index above 0.
+         * Attribute is resident, implying it is not compressed, encrypted, or
+         * mst protected.  This also means the attribute is smaller than an mft
+         * record and hence smaller than a page, so can simply return error on
+         * any pages with index above 0.  Note the attribute can actually be
+         * marked compressed but if it is resident the actual data is not
+         * compressed so we are ok to ignore the compressed flag here.
          */
         BUG_ON(page_has_buffers(page));
         BUG_ON(!PageUptodate(page));
@@ -1401,30 +1407,14 @@ retry_writepage:
         BUG_ON(PageWriteback(page));
         set_page_writeback(page);
         unlock_page(page);
-
         /*
-         * Here, we don't need to zero the out of bounds area everytime because
-         * the below memcpy() already takes care of the mmap-at-end-of-file
-         * requirements. If the file is converted to a non-resident one, then
-         * the code path use is switched to the non-resident one where the
-         * zeroing happens on each ntfs_writepage() invocation.
-         *
-         * The above also applies nicely when i_size is decreased.
-         *
-         * When i_size is increased, the memory between the old and new i_size
-         * _must_ be zeroed (or overwritten with new data). Otherwise we will
-         * expose data to userspace/disk which should never have been exposed.
-         *
-         * FIXME: Ensure that i_size increases do the zeroing/overwriting and
-         * if we cannot guarantee that, then enable the zeroing below.  If the
-         * zeroing below is enabled, we MUST move the unlock_page() from above
-         * to after the kunmap_atomic(), i.e. just before the
-         * end_page_writeback().
-         * UPDATE: ntfs_prepare/commit_write() do the zeroing on i_size
-         * increases for resident attributes so those are ok.
-         * TODO: ntfs_truncate(), others?
+         * Here, we do not need to zero the out of bounds area everytime
+         * because the below memcpy() already takes care of the
+         * mmap-at-end-of-file requirements.  If the file is converted to a
+         * non-resident one, then the code path use is switched to the
+         * non-resident one where the zeroing happens on each ntfs_writepage()
+         * invocation.
          */
-
         attr_len = le32_to_cpu(ctx->attr->data.resident.value_length);
         i_size = i_size_read(vi);
         if (unlikely(attr_len > i_size)) {