There is a bug in commit c8d46e41 "ext4: Add flag to files with blocks
intentionally past EOF" that if we fallocate a file with FALLOC_FL_KEEP_SIZE
flag and then ftruncate the file to a size larger than the file's i_size,
any allocated but unwritten blocks will be freed but the file size is set
to the size that ftruncate specifies.
Here is a simple test to reproduce the problem:
1. fallocate a 12k size file with KEEP_SIZE flag
2. write the first 4k
3. ftruncate the file to 8k
Then 'ls -l' shows that the i_size of the file becomes 8k but debugfs
shows the file has only the first written block left.
Below is the proposed patch to fix the bug:
ext4: use vmtruncate() instead of ext4_truncate() in ext4_setattr().
Change ext4_setattr() to use vmtruncate(inode, attr->ia_size) instead
of ext4_truncate(inode) when it needs to truncate an inode so that
if the inode has EXT4_EOFBLOCKS_FL flag set and we are trying to truncate
to a size larger than the inode's i_size, we will only truncate the blocks
beyond the specified truncate size instead of all of blocks beyond i_size.
Signed-off-by: Jiaying Zhang <jiayingz@xxxxxxxxxx>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3424e82..3bfad57 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5347,8 +5347,11 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
}
}
/* ext4_truncate will clear the flag */
- if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)))
- ext4_truncate(inode);
+ if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))) {
+ rc = vmtruncate(inode, attr->ia_size);
+ if (rc)
+ goto err_out;
+ }
}
if ((attr->ia_valid & ATTR_SIZE) &&
--
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