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* [PATCH 00/31] Remove iget() and read_inode() [try #5]
@ 2007-10-25 16:33 David Howells
  2007-10-25 16:33 ` [PATCH 01/31] Add an ERR_CAST() macro to complement ERR_PTR and co. " David Howells
                   ` (30 more replies)
  0 siblings, 31 replies; 39+ messages in thread
From: David Howells @ 2007-10-25 16:33 UTC (permalink / raw)
  To: akpm; +Cc: linux-kernel, linux-fsdevel, dhowells



Here's a set of patches that remove all calls to iget() and all read_inode()
functions.  They should be removed for two reasons: firstly they don't lend
themselves to good error handling, and secondly their presence is a temptation
for code outside a filesystem to call iget() to access inodes within that
filesystem.

There are a few benefits to this:

 (1) Error handling gets simpler as you can return an error code rather than
     having to call is_bad_inode().

 (2) You can now tell the difference between ENOMEM and EIO occurring in the
     read_inode() path.

 (3) The code should get smaller.  iget() is an inline function that is
     typically called 2-3 times per filesystem that uses it.  By folding the
     iget code into the read_inode code for each filesystem, it eliminates
     some duplication.

A tarball of the patches can be retrieved from:

	http://people.redhat.com/~dhowells/iget-remove.tar.bz2


Additionally, there are a couple of patches that introduce an ERR_CAST() macro
to be used instead of ERR_PTR(PTR_ERR(p)) constructs and apply it to all such
instances in the kernel.

Of the patches directly relevant to the subject:

The first patch adds a function, iget_failed() that is a canned piece of code
for killing an inode when the inode construction path fails.

The second and third patches makes AFS and GFS2 use iget_failed() rather than
interpolating the sequence directly.

The final patch removes iget() and read_inode().

Each of the other patches modify a filesystem that used iget() and read_inode()
to use iget_locked() instead.  The standard procedure was to convert:

	void thingyfs_read_inode(struct inode *inode)
	{
		...
	}

into:

	struct inode *thingyfs_iget(struct super_block *sp, unsigned long ino)
	{
		struct inode *inode;
		int ret;
		
		inode = iget_locked(sb, ino);
		if (!inode)
			return ERR_PTR(-ENOMEM);
		if (!(inode->i_state & I_NEW))
			return inode;

		...
		unlock_new_inode(inode);
		return inode;
	error:
		iget_failed(inode);
		return ERR_PTR(ret);
	}

and then call thingyfs_iget() rather than iget():

	ret = -EINVAL;
	inode = iget(sb, ino);
	if (!inode || is_bad_inode(inode))
		goto error;

becomes:

	inode = thingyfs_iget(sb, ino);
	if (IS_ERR(inode)) {
		ret = PTR_ERR(inode);
		goto error;
	}

There were exceptions; most notably it appeared FAT should be calling ilookup()
not iget().

Additionally, HPPFS and HOSTFS (UM-specific filesystems) really need checking:

 hostfs_kern.c:

 (*) hostfs_iget() should perhaps subsume init_inode() and hostfs_read_inode().

 (*) It would appear that all hostfs inodes are the same inode because iget()
     was being called with inode number 0 - which forms the lookup key.

 hppfs_kern.c:

 (*) The HPPFS inode retains a pointer to the proc dentry it is shadowing, but
     whilst it does appear to retain a reference to it, it doesn't appear to
     destroy the reference if the inode goes away.

 (*) hppfs_iget() should perhaps subsume init_inode() and hppfs_read_inode().

 (*) It would appear that all hppfs inodes are the same inode because iget()
     was being called with inode number 0, which forms the lookup key.

David

^ permalink raw reply	[flat|nested] 39+ messages in thread

end of thread, other threads:[~2007-11-06 11:13 UTC | newest]

Thread overview: 39+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2007-10-25 16:33 [PATCH 00/31] Remove iget() and read_inode() [try #5] David Howells
2007-10-25 16:33 ` [PATCH 01/31] Add an ERR_CAST() macro to complement ERR_PTR and co. " David Howells
2007-10-25 23:09   ` Zach Brown
2007-10-25 23:38     ` Roland Dreier
2007-10-26  0:20       ` Zach Brown
2007-10-25 23:46     ` Andrew Morton
2007-10-25 16:34 ` [PATCH 02/31] Convert ERR_PTR(PTR_ERR(p)) instances to ERR_CAST(p) " David Howells
2007-10-25 16:34 ` [PATCH 03/31] IGET: Introduce a function to register iget failure " David Howells
2007-10-25 16:34 ` [PATCH 04/31] IGET: Use iget_failed() in AFS " David Howells
2007-10-25 16:34 ` [PATCH 05/31] IGET: Use iget_failed() in GFS2 " David Howells
2007-10-25 16:34 ` [PATCH 06/31] IGET: Stop AFFS from using iget() and read_inode() " David Howells
2007-10-25 16:34 ` [PATCH 07/31] IGET: Stop autofs " David Howells
2007-10-25 16:34 ` [PATCH 08/31] IGET: Stop BEFS " David Howells
2007-10-25 16:34 ` [PATCH 09/31] IGET: Stop BFS " David Howells
2007-10-25 16:34 ` [PATCH 10/31] IGET: Stop CIFS " David Howells
2007-10-25 16:34 ` [PATCH 11/31] IGET: Stop EFS " David Howells
2007-10-25 16:34 ` [PATCH 12/31] IGET: Stop EXT2 " David Howells
2007-10-25 16:34 ` [PATCH 13/31] IGET: Stop EXT3 " David Howells
2007-10-25 16:35 ` [PATCH 14/31] IGET: Stop EXT4 " David Howells
2007-10-25 16:35 ` [PATCH 15/31] IGET: Stop FAT " David Howells
2007-10-25 16:35 ` [PATCH 16/31] IGET: Stop FreeVXFS " David Howells
2007-11-06 10:25   ` Andrew Morton
2007-11-06 11:09   ` David Howells
2007-11-06 11:13   ` David Howells
2007-10-25 16:35 ` [PATCH 17/31] IGET: Stop FUSE " David Howells
2007-10-25 16:35 ` [PATCH 18/31] IGET: Stop HFSPLUS " David Howells
2007-10-25 16:35 ` [PATCH 19/31] IGET: Stop ISOFS from using " David Howells
2007-10-25 16:35 ` [PATCH 20/31] IGET: Stop JFFS2 from using iget() and " David Howells
2007-10-25 16:35 ` [PATCH 21/31] IGET: Stop JFS " David Howells
2007-10-25 16:35 ` [PATCH 22/31] IGET: Stop the MINIX filesystem " David Howells
2007-10-25 16:35 ` [PATCH 23/31] IGET: Stop PROCFS " David Howells
2007-10-25 16:36 ` [PATCH 24/31] IGET: Stop QNX4 " David Howells
2007-10-25 16:36 ` [PATCH 25/31] IGET: Stop ROMFS " David Howells
2007-10-25 16:36 ` [PATCH 26/31] IGET: Stop the SYSV filesystem " David Howells
2007-10-25 16:36 ` [PATCH 27/31] IGET: Stop UFS " David Howells
2007-10-25 16:36 ` [PATCH 28/31] IGET: Stop OPENPROMFS " David Howells
2007-10-25 16:36 ` [PATCH 29/31] IGET: Stop HOSTFS " David Howells
2007-10-25 16:36 ` [PATCH 30/31] IGET: Stop HPPFS " David Howells
2007-10-25 16:36 ` [PATCH 31/31] IGET: Remove iget() and the read_inode() super op as being obsolete " David Howells

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