linux-ext4 - Is EXT4_FITS_IN

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Message-ID: <25591.1446743937@warthog.procyon.org.uk>
Date:	Thu, 05 Nov 2015 17:18:57 +0000
From:	David Howells <dhowells@...hat.com>
To:	linux-ext4@...r.kernel.org
cc:	dhowells@...hat.com
Subject: Is EXT4_FITS_IN_INODE() broken?

Is EXT4_FITS_IN_INODE() broken?  It makes use of i_extra_isize - which is an
optional field and doesn't exist if the filesystem was made with "-I 128".

	(gdb) p &((struct ext4_inode *)0)->i_extra_isize
	$2 = (__le16 *) 0x80 <irq_stack_union+128>

Should EXT4_FITS_IN_INODE():

	#define EXT4_FITS_IN_INODE(ext4_inode, einode, field)	\
		((offsetof(typeof(*ext4_inode), field) +	\
		  sizeof((ext4_inode)->field))			\
		<= (EXT4_GOOD_OLD_INODE_SIZE +			\
		    (einode)->i_extra_isize))			\

be using EXT4_INODE_SIZE() and consulting the superblock instead?

David
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