From 9e28059d56649a7212d5b3f8751ec021154ba3dd Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 7 Feb 2025 23:08:02 -0500 Subject: ext4: introduce linear search for dentries MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch addresses an issue where some files in case-insensitive directories become inaccessible due to changes in how the kernel function, utf8_casefold(), generates case-folded strings from the commit 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points"). There are good reasons why this change should be made; it's actually quite stupid that Unicode seems to think that the characters ❤ and ❤️ should be casefolded. Unfortimately because of the backwards compatibility issue, this commit was reverted in 231825b2e1ff. This problem is addressed by instituting a brute-force linear fallback if a lookup fails on case-folded directory, which does result in a performance hit when looking up files affected by the changing how thekernel treats ignorable Uniode characters, or when attempting to look up non-existent file names. So this fallback can be disabled by setting an encoding flag if in the future, the system administrator or the manufacturer of a mobile handset or tablet can be sure that there was no opportunity for a kernel to insert file names with incompatible encodings. Fixes: 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points") Signed-off-by: Theodore Ts'o Reviewed-by: Gabriel Krisman Bertazi --- include/linux/fs.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 2c3b2f8a621f..aa4ec39202c3 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1258,11 +1258,19 @@ extern int send_sigurg(struct file *file); #define SB_NOUSER BIT(31) /* These flags relate to encoding and casefolding */ -#define SB_ENC_STRICT_MODE_FL (1 << 0) +#define SB_ENC_STRICT_MODE_FL (1 << 0) +#define SB_ENC_NO_COMPAT_FALLBACK_FL (1 << 1) #define sb_has_strict_encoding(sb) \ (sb->s_encoding_flags & SB_ENC_STRICT_MODE_FL) +#if IS_ENABLED(CONFIG_UNICODE) +#define sb_no_casefold_compat_fallback(sb) \ + (sb->s_encoding_flags & SB_ENC_NO_COMPAT_FALLBACK_FL) +#else +#define sb_no_casefold_compat_fallback(sb) (1) +#endif + /* * Umount options */ -- cgit v1.2.3