NTFS: Initial implementation of write(2) based overwriting of existing

files on ntfs. (Note: Resident files are not supported yet, so avoid
writing to files smaller than 1kiB.)

Documentation/filesystems/ntfs.txt

@@ -247,6 +247,11 @@ ChangeLog
 
 Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.
 
+2.1.0:
+	- Add configuration option for developmental write support.
+	- Initial implementation of file overwriting. (Writes to resident files
+	  are not written out to disk yet, so avoid writing to files smaller
+	  than about 1kiB.)
 2.0.25:
 	- Minor bugfixes in error code paths and small cleanups.
 2.0.24:

fs/ntfs/ChangeLog

 ToDo:
 	- Find and fix bugs.
 	- Enable NFS exporting of NTFS.
+	- Implement aops->set_page_dirty() in order to take control of buffer
+	  dirtying. Not having it means if page_has_buffers(), all buffers
+	  will be dirtied with the page. And if not they won't be. That is
+	  fine for the moment but will break once we enable metadata updates.
+	- Implement sops->dirty_inode() to implement {a,m,c} time updates and
+	  such things.
+	- Implement sops->write_inode().
+	- In between ntfs_prepare/commit_write, need exclusion between
+	  simultaneous file extensions. Need perhaps an NInoResizeUnderway()
+	  flag which we can set in ntfs_prepare_write() and clear again in
+	  ntfs_commit_write(). Just have to be careful in readpage/writepage,
+	  as well as in truncate, that we play nice... We might need to have
+	  a data_size field in the ntfs_inode to store the real attribute
+	  length. Also need to be careful with initialized_size extention in
+	  ntfs_prepare_write. Basically, just be _very_ careful in this code...
+	  OTOH, perhaps i_sem, which is held accross generic_file_write is
+	  sufficient for synchronisation here. We then just need to make sure
+	  ntfs_readpage/writepage/truncate interoperate properly with us.
+
+2.1.0 - First steps towards write support: implement file overwrite.
+
+	- Add configuration option for developmental write support with an
+	  appropriately scary configuration help text.
+	- Initial implementation of fs/ntfs/aops.c::ntfs_writepage() and its
+	  helper fs/ntfs/aops.c::ntfs_write_block(). This enables mmap(2) based
+	  overwriting of existing files on ntfs. Note: Resident files are
+	  only written into memory, and not written out to disk at present, so
+	  avoid writing to files smaller than about 1kiB.
+	- Initial implementation of fs/ntfs/aops.c::ntfs_prepare_write(), its
+	  helper fs/ntfs/aops.c::ntfs_prepare_nonresident_write() and their
+	  counterparts, fs/ntfs/aops.c::ntfs_commit_write(), and
+	  fs/ntfs/aops.c::ntfs_commit_nonresident_write(), respectively. Also,
+	  add generic_file_write() to the ntfs file operations (fs/ntfs/file.c).
+	  This enables write(2) based overwriting of existing files on ntfs.
+	  Note: As with mmap(2) based overwriting, resident files are only
+	  written into memory, and not written out to disk at present, so avoid
+	  writing to files smaller than about 1kiB.
 
 2.0.25 - Small bug fixes and cleanups.
 

fs/ntfs/attrib.c

@@ -1182,8 +1182,9 @@ BOOL find_attr(const ATTR_TYPES type, const uchar_t *name, const u32 name_len,
 		else {
 			register int rc;
 			
-			rc = memcmp(val, (u8*)a +le16_to_cpu(a->_ARA(value_offset)),
-				min(val_len, le32_to_cpu(a->_ARA(value_length))));
+			rc = memcmp(val, (u8*)a + le16_to_cpu(
+					a->_ARA(value_offset)), min(val_len,
+					le32_to_cpu(a->_ARA(value_length))));
 			/*
 			 * If @val collates before the current attribute's
 			 * value, there is no matching attribute.

fs/ntfs/file.c

@@ -51,6 +51,9 @@ static int ntfs_file_open(struct inode *vi, struct file *filp)
 struct file_operations ntfs_file_ops = {
 	.llseek		= generic_file_llseek,	/* Seek inside file. */
 	.read		= generic_file_read,	/* Read from file. */
+#ifdef NTFS_RW
+	.write		= generic_file_write,	/* Write to a file. */
+#endif
 	.mmap		= generic_file_mmap,	/* Mmap file. */
 	.sendfile	= generic_file_sendfile,/* Zero-copy data send with the
 						   data source being on the

fs/ntfs/mft.c

@@ -98,7 +98,7 @@ int format_mft_record(ntfs_inode *ni, MFT_RECORD *mft_rec)
 }
 
 /**
- * From fs/ntfs/aops.c
+ * ntfs_readpage - external declaration, function is in fs/ntfs/aops.c
  */
 extern int ntfs_readpage(struct file *, struct page *);
 
@@ -109,12 +109,9 @@ extern int ntfs_readpage(struct file *, struct page *);
  * ntfs_map_page() in map_mft_record_page().
  */
 struct address_space_operations ntfs_mft_aops = {
-	.writepage	= NULL,			/* Write dirty page to disk. */
 	.readpage	= ntfs_readpage,	/* Fill page with data. */
 	.sync_page	= block_sync_page,	/* Currently, just unplugs the
 						   disk request queue. */
-	.prepare_write	= NULL,			/* . */
-	.commit_write	= NULL,			/* . */
 };
 
 /**

fs/ntfs/mft.h

@@ -43,5 +43,19 @@ static inline void unmap_extent_mft_record(ntfs_inode *ni)
 	return;
 }
 
+/*
+ * flush_dcache_mft_record_page - flush_dcache_page() for mft records
+ * @ni:		ntfs inode structure of mft record
+ *
+ * Call flush_dcache_page() for the page in which an mft record resides.
+ *
+ * This must be called every time an mft record is modified, just after the
+ * modification.
+ */
+static inline void flush_dcache_mft_record_page(ntfs_inode *ni)
+{
+	flush_dcache_page(ni->page);
+}
+
 #endif /* _LINUX_NTFS_MFT_H */