ext4: Add flag to files with blocks intentionally past EOF

fallocate() may potentially instantiate blocks past EOF, depending
on the flags used when it is called.

e2fsck currently has a test for blocks past i_size, and it
sometimes trips up - noticeably on xfstests 013 which runs fsstress.

This patch from Jiayang does fix it up - it (along with
e2fsprogs updates and other patches recently from Aneesh) has
survived many fsstress runs in a row.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -285,10 +285,11 @@ struct flex_groups {
 #define EXT4_HUGE_FILE_FL               0x00040000 /* Set to each huge file */
 #define EXT4_EXTENTS_FL			0x00080000 /* Inode uses extents */
 #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
+#define EXT4_EOFBLOCKS_FL		0x00400000 /* Blocks allocated beyond EOF */
 #define EXT4_RESERVED_FL		0x80000000 /* reserved for ext4 lib */
 
-#define EXT4_FL_USER_VISIBLE		0x000BDFFF /* User visible flags */
+#define EXT4_FL_USER_VISIBLE		0x004BDFFF /* User visible flags */
-#define EXT4_FL_USER_MODIFIABLE		0x000B80FF /* User modifiable flags */
+#define EXT4_FL_USER_MODIFIABLE		0x004B80FF /* User modifiable flags */
 
 /* Flags that should be inherited by new inodes from their parent. */
 #define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\

fs/ext4/extents.c

@@ -3186,7 +3186,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 {
 	struct ext4_ext_path *path = NULL;
 	struct ext4_extent_header *eh;
-	struct ext4_extent newex, *ex;
+	struct ext4_extent newex, *ex, *last_ex;
 	ext4_fsblk_t newblock;
 	int err = 0, depth, ret, cache_type;
 	unsigned int allocated = 0;
@@ -3367,6 +3367,19 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 						     EXT4_STATE_DIO_UNWRITTEN);
 		}
 	}
+
+	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EOFBLOCKS_FL)) {
+		if (eh->eh_entries) {
+			last_ex = EXT_LAST_EXTENT(eh);
+			if (iblock + ar.len > le32_to_cpu(last_ex->ee_block)
+					    + ext4_ext_get_actual_len(last_ex))
+				EXT4_I(inode)->i_flags &= ~EXT4_EOFBLOCKS_FL;
+		} else {
+			WARN_ON(eh->eh_entries == 0);
+			ext4_error(inode->i_sb, __func__,
+				"inode#%lu, eh->eh_entries = 0!", inode->i_ino);
+			}
+	}
 	err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
 	if (err) {
 		/* free data blocks we just allocated */
@@ -3500,6 +3513,13 @@ static void ext4_falloc_update_inode(struct inode *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_I(inode)->i_flags |= EXT4_EOFBLOCKS_FL;
 	}
 
 }

fs/ext4/inode.c

@@ -4456,6 +4456,8 @@ void ext4_truncate(struct inode *inode)
 	if (!ext4_can_truncate(inode))
 		return;
 
+	EXT4_I(inode)->i_flags &= ~EXT4_EOFBLOCKS_FL;
+
 	if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
 		ext4_set_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
 
@@ -5305,7 +5307,9 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 	}
 
 	if (S_ISREG(inode->i_mode) &&
-	    attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
+	    attr->ia_valid & ATTR_SIZE &&
+	    (attr->ia_size < inode->i_size ||
+	     (EXT4_I(inode)->i_flags & EXT4_EOFBLOCKS_FL))) {
 		handle_t *handle;
 
 		handle = ext4_journal_start(inode, 3);
@@ -5336,6 +5340,9 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 				goto err_out;
 			}
 		}
+		/* ext4_truncate will clear the flag */
+		if ((EXT4_I(inode)->i_flags & EXT4_EOFBLOCKS_FL))
+			ext4_truncate(inode);
 	}
 
 	rc = inode_setattr(inode, attr);

fs/ext4/ioctl.c

@@ -92,6 +92,15 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			flags &= ~EXT4_EXTENTS_FL;
 		}
 
+		if (flags & EXT4_EOFBLOCKS_FL) {
+			/* we don't support adding EOFBLOCKS flag */
+			if (!(oldflags & EXT4_EOFBLOCKS_FL)) {
+				err = -EOPNOTSUPP;
+				goto flags_out;
+			}
+		} else if (oldflags & EXT4_EOFBLOCKS_FL)
+			ext4_truncate(inode);
+
 		handle = ext4_journal_start(inode, 1);
 		if (IS_ERR(handle)) {
 			err = PTR_ERR(handle);