Re: [PATCH] ext4: compensate ea_inode refs and free block on new xattr block write error

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The patch introduces calls to `mb_cache_entry_delete_or_get()` and `mb_cache_entry_wait_unused()`, which are not defined anywhere in the Linux kernel codebase. This will cause compilation and linking failures due to implicit function declarations and undefined symbols.
--

--- Patch [1]: [PATCH] ext4: compensate ea_inode refs and free block on new xattr block write error ---
commit 867eb1668b3595297e1515877804d2ee15fc4038
Author: Matthias Goergens <matthias.goergens@gmail.com>

ext4: compensate ea_inode refs and free block on new xattr block write error

This commit adds error handling in ext4_xattr_block_set() to properly revert
the on-disk reference counts and free the newly allocated xattr block if
metadata dirtying fails. It introduces ext4_xattr_new_block_fail() to handle
mbcache cleanup, block freeing, and quota release.

Link: https://lore.kernel.org/linux-ext4/20260814070432.595B91F00A3A@smtp.kernel.org/

> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index 6127e94ea4f5d..f49d1e74e3214 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c

[ ... ]

> @@ -1299,6 +1299,63 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
>  	return;
>  }
>  
> +/*
> + * Undo the setup of a new xattr block that failed to be written out: drop
> + * the ext4_xattr_inode_inc_ref_all() references, free the block, and
> + * release the quota this operation charged for the new value (quota_len,
> + * zero when the value is not in an EA inode).
> + */
> +static void ext4_xattr_new_block_fail(handle_t *handle, struct inode *inode,
> +				      struct buffer_head *new_bh,
> +				      size_t quota_len, int error)
> +{

[ ... ]

> +	lock_buffer(new_bh);
> +retry_owner:
> +	if (le32_to_cpu(BHDR(new_bh)->h_refcount) != 1) {
> +		unlock_buffer(new_bh);
> +		return;
> +	}
> +	if (ea_block_cache) {
> +		oe = mb_cache_entry_delete_or_get(ea_block_cache,
> +						  le32_to_cpu(BHDR(new_bh)->h_hash),
> +						  new_bh->b_blocknr);
> +		if (oe) {
> +			unlock_buffer(new_bh);
> +			mb_cache_entry_wait_unused(oe);

[Severity: Low]
Are mb_cache_entry_delete_or_get() and mb_cache_entry_wait_unused() defined
anywhere in the kernel codebase?

Building the kernel with EXT4 support enabled will likely fail to compile
or link because these required mbcache functions appear to be missing.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260817095421.1171145-1-matthias.goergens@gmail.com?part=1