linux-kernel - Re: [PATCH] fs/hpfs: Fix error code for new_inode() failure in mkdir/create/mknod/symlink

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Message-ID: <20250504032355.GB2023217@ZenIV>
Date: Sun, 4 May 2025 04:23:55 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: yikangy2@...inois.edu
Cc: mikulas@...ax.karlin.mff.cuni.cz, linux-kernel@...r.kernel.org,
	shaobol2@...inois.edu, yiruiz2@...inois.edu, jianh@...inois.edu
Subject: Re: [PATCH] fs/hpfs: Fix error code for new_inode() failure in
 mkdir/create/mknod/symlink

On Sat, May 03, 2025 at 08:44:34PM -0500, yikangy2@...inois.edu wrote:
> From: Yikang Yue <yikangy2@...inois.edu>
> 
> The function call new_inode() is a primitive for allocating an inode in memory,
> rather than planning disk space for it. Therefore, -ENOMEM should be returned
> as the error code rather than -ENOSPC.
> 
> To be specific, new_inode()'s call path looks like this:
> new_inode
>   new_inode_pseudo
>     alloc_inode
>       ops->alloc_inode (hpfs_alloc_inode)
>         alloc_inode_sb
>           kmem_cache_alloc_lru
> 
> Therefore, the failure of new_inode() indicates a memory presure issue (-ENOMEM),
> not a lack of disk space. However, the current implementation of
> hpfs_mkdir/create/mknod/symlink incorrectly returns -ENOSPC when new_inode() fails.
> This patch fix this by set err to -ENOMEM before the goto statement.
> 
> BTW, we also noticed that other nested calls within these four functions,
> like hpfs_alloc_f/dnode and hpfs_add_dirent, might also fail due to memory presure.
> But similarly, only -ENOSPC is returned. Addressing these will involve code
> modifications in other functions, and we plan to submit dedicated patches for these
> issues in the future. For this patch, we focus on new_inode().

Frankly, that amount of boilerplate is begging for a helper function...