ext4: Update inode i_size after the preallocation

Currently in ext4_fallocate we would update inode size, c_time and sync
the file with every partial allocation which is entirely unnecessary. It
is true that if the crash happens in the middle of truncate we might end
up with unchanged i size, or c_time which I do not think is really a
problem - it does not mean file system corruption in any way. Note that
xfs is doing things the same way e.g. update all of the mentioned after
the allocation is done.

This commit moves all the updates after the allocation is done. In
addition we also need to change m_time as not only inode has been change
bot also data regions might have changed (unwritten extents). However
m_time will be only updated when i_size changed.

Also we do not need to be paranoid about changing the c_time only if the
actual allocation have happened, we can change it even if we try to
allocate only to find out that there are already block allocated. It's
not really a big deal and it will save us some additional complexity.

Also use ext4_debug, instead of ext4_warning in #ifdef EXT4FS_DEBUG
section.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>-
--
v3: Do not remove the code to set EXT4_INODE_EOFBLOCKS flag

 fs/ext4/extents.c | 96 ++++++++++++++++++++++++-------------------------------
 1 file changed, 42 insertions(+), 54 deletions(-)

fs/ext4/extents.c

@@ -4546,36 +4546,6 @@ void ext4_ext_truncate(handle_t *handle, struct inode *inode)
 	ext4_std_error(inode->i_sb, err);
 }
 
-static void ext4_falloc_update_inode(struct inode *inode,
-				int mode, loff_t new_size, int update_ctime)
-{
-	struct timespec now;
-
-	if (update_ctime) {
-		now = current_fs_time(inode->i_sb);
-		if (!timespec_equal(&inode->i_ctime, &now))
-			inode->i_ctime = now;
-	}
-	/*
-	 * Update only when preallocation was requested beyond
-	 * the file size.
-	 */
-	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
-		if (new_size > i_size_read(inode))
-			i_size_write(inode, new_size);
-		if (new_size > EXT4_I(inode)->i_disksize)
-			ext4_update_i_disksize(inode, new_size);
-	} else {
-		/*
-		 * Mark that we allocate beyond EOF so the subsequent truncate
-		 * can proceed even if the new size is the same as i_size.
-		 */
-		if (new_size > i_size_read(inode))
-			ext4_set_inode_flag(inode, EXT4_INODE_EOFBLOCKS);
-	}
-
-}
-
 /*
  * preallocate space for a file. This implements ext4's fallocate file
  * operation, which gets called from sys_fallocate system call.
@@ -4587,13 +4557,14 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 {
 	struct inode *inode = file_inode(file);
 	handle_t *handle;
-	loff_t new_size;
+	loff_t new_size = 0;
 	unsigned int max_blocks;
 	int ret = 0;
 	int ret2 = 0;
 	int retries = 0;
 	int flags;
 	struct ext4_map_blocks map;
+	struct timespec tv;
 	unsigned int credits, blkbits = inode->i_blkbits;
 
 	/* Return error if mode is not supported */
@@ -4631,12 +4602,15 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	 */
 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
 	mutex_lock(&inode->i_mutex);
-	ret = inode_newsize_ok(inode, (len + offset));
-	if (ret) {
-		mutex_unlock(&inode->i_mutex);
-		trace_ext4_fallocate_exit(inode, offset, max_blocks, ret);
-		return ret;
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
+	     offset + len > i_size_read(inode)) {
+		new_size = offset + len;
+		ret = inode_newsize_ok(inode, new_size);
+		if (ret)
+			goto out;
 	}
+
 	flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT;
 	if (mode & FALLOC_FL_KEEP_SIZE)
 		flags |= EXT4_GET_BLOCKS_KEEP_SIZE;
@@ -4660,28 +4634,14 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 		}
 		ret = ext4_map_blocks(handle, inode, &map, flags);
 		if (ret <= 0) {
-#ifdef EXT4FS_DEBUG
-			ext4_warning(inode->i_sb,
-				     "inode #%lu: block %u: len %u: "
-				     "ext4_ext_map_blocks returned %d",
-				     inode->i_ino, map.m_lblk,
-				     map.m_len, ret);
-#endif
+			ext4_debug("inode #%lu: block %u: len %u: "
+				   "ext4_ext_map_blocks returned %d",
+				   inode->i_ino, map.m_lblk,
+				   map.m_len, ret);
 			ext4_mark_inode_dirty(handle, inode);
 			ret2 = ext4_journal_stop(handle);
 			break;
 		}
-		if ((map.m_lblk + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
-						blkbits) >> blkbits))
-			new_size = offset + len;
-		else
-			new_size = ((loff_t) map.m_lblk + ret) << blkbits;
-
-		ext4_falloc_update_inode(inode, mode, new_size,
-					 (map.m_flags & EXT4_MAP_NEW));
-		ext4_mark_inode_dirty(handle, inode);
-		if ((file->f_flags & O_SYNC) && ret >= max_blocks)
-			ext4_handle_sync(handle);
 		ret2 = ext4_journal_stop(handle);
 		if (ret2)
 			break;
@@ -4691,6 +4651,34 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 		ret = 0;
 		goto retry;
 	}
+
+	handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
+	if (IS_ERR(handle))
+		goto out;
+
+	tv = inode->i_ctime = ext4_current_time(inode);
+
+	if (ret > 0 && new_size) {
+		if (new_size > i_size_read(inode)) {
+			i_size_write(inode, new_size);
+			inode->i_mtime = tv;
+		}
+		if (new_size > EXT4_I(inode)->i_disksize)
+			ext4_update_i_disksize(inode, new_size);
+	} else if (ret > 0 && !new_size) {
+		/*
+		* Mark that we allocate beyond EOF so the subsequent truncate
+		* can proceed even if the new size is the same as i_size.
+		*/
+		if ((offset + len) > i_size_read(inode))
+			ext4_set_inode_flag(inode, EXT4_INODE_EOFBLOCKS);
+	}
+	ext4_mark_inode_dirty(handle, inode);
+	if (file->f_flags & O_SYNC)
+		ext4_handle_sync(handle);
+
+	ext4_journal_stop(handle);
+out:
 	mutex_unlock(&inode->i_mutex);
 	trace_ext4_fallocate_exit(inode, offset, max_blocks,
 				ret > 0 ? ret2 : ret);