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Wed, 12 Feb 2025 21:02:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id B31qG2MMrWewMgAAD6G6ig (envelope-from ); Wed, 12 Feb 2025 21:02:27 +0000 From: Gabriel Krisman Bertazi To: "Theodore Ts'o" Cc: Ext4 Developers List , drosen@google.com Subject: Re: [PATCH] ext4: introduce linear search for dentries In-Reply-To: <20250212164448.111211-1-tytso@mit.edu> (Theodore Ts'o's message of "Wed, 12 Feb 2025 11:44:48 -0500") Organization: SUSE References: <20250212164448.111211-1-tytso@mit.edu> Date: Wed, 12 Feb 2025 16:02:21 -0500 Message-ID: <87h64yx4f6.fsf@mailhost.krisman.be> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; HAS_ORG_HEADER(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email] X-Spam-Score: -4.30 X-Spam-Flag: NO "Theodore Ts'o" writes: > 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 =E2=9D=A4 an= d =E2=9D=A4=EF=B8=8F > 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 --=20 Gabriel Krisman Bertazi