linux-kernel - Re: [RESEND PATCH v9 2/3] ext4: Reuse generic_ci

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Message-ID: <87plx6vlu9.fsf@mailhost.krisman.be>
Date: Thu, 08 Feb 2024 13:42:54 -0500
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: Eugen Hristev <eugen.hristev@...labora.com>
Cc: tytso@....edu,  adilger.kernel@...ger.ca,  jaegeuk@...nel.org,
  chao@...nel.org,  viro@...iv.linux.org.uk,  brauner@...nel.org,
  linux-ext4@...r.kernel.org,  linux-f2fs-devel@...ts.sourceforge.net,
  jack@...e.cz,  linux-kernel@...r.kernel.org,
  linux-fsdevel@...r.kernel.org,  kernel@...labora.com,  Gabriel Krisman
 Bertazi <krisman@...labora.com>
Subject: Re: [RESEND PATCH v9 2/3] ext4: Reuse generic_ci_match for ci
 comparisons

Eugen Hristev <eugen.hristev@...labora.com> writes:

>  int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
>  				  struct ext4_filename *name)
>  {
> @@ -1503,20 +1451,35 @@ static bool ext4_match(struct inode *parent,
>  #if IS_ENABLED(CONFIG_UNICODE)
>  	if (IS_CASEFOLDED(parent) &&
>  	    (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
> -		if (fname->cf_name.name) {
> -			if (IS_ENCRYPTED(parent)) {
> -				if (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
> -					fname->hinfo.minor_hash !=
> -						EXT4_DIRENT_MINOR_HASH(de)) {
> +		int ret;
>  
> -					return false;
> -				}
> -			}
> -			return !ext4_ci_compare(parent, &fname->cf_name,
> -						de->name, de->name_len, true);
> +		/*
> +		 * Just checking IS_ENCRYPTED(parent) below is not
> +		 * sufficient to decide whether one can use the hash for
> +		 * skipping the string comparison, because the key might
> +		 * have been added right after
> +		 * ext4_fname_setup_ci_filename().  In this case, a hash
> +		 * mismatch will be a false negative.  Therefore, make
> +		 * sure cf_name was properly initialized before
> +		 * considering the calculated hash.
> +		 */
> +		if (IS_ENCRYPTED(parent) && fname->cf_name.name &&
> +		    (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
> +		     fname->hinfo.minor_hash != EXT4_DIRENT_MINOR_HASH(de)))
> +			return false;
> +
> +		ret = generic_ci_match(parent, fname->usr_fname,
> +				       &fname->cf_name, de->name,
> +				       de->name_len);
> +		if (ret < 0) {
> +			/*
> +			 * Treat comparison errors as not a match.  The
> +			 * only case where it happens is on a disk
> +			 * corruption or ENOMEM.
> +			 */
> +			return false;

A minor problem with splitting the series as you did is that "ext4: Log
error when lookup of encoded dentry fails" conflicts with this change
and you get a merge conflict if it is applied in the wrong order.

-- 
Gabriel Krisman Bertazi