kernel/linux.git/fs/ext4/hash.c, branch v6.12.80

ext4: remove redundant checks of s_encoding

2023-08-27T15:27:13+00:00

Now that ext4 does not allow inodes with the casefold flag to be instantiated when unsupported, it's unnecessary to repeatedly check for support later on during random filesystem operations. Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/20230814182903.37267-3-ebiggers@kernel.org Signed-off-by: Theodore Ts'o

ext4: improve error handling from ext4_dirhash()

2023-05-13T22:05:05+00:00

The ext4_dirhash() will *almost* never fail, especially when the hash tree feature was first introduced. However, with the addition of support of encrypted, casefolded file names, that function can most certainly fail today. So make sure the callers of ext4_dirhash() properly check for failures, and reflect the errors back up to their callers. Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230506142419.984260-1-tytso@mit.edu Reported-by: syzbot+394aa8a792cb99dbc837@syzkaller.appspotmail.com Reported-by: syzbot+344aaa8697ebd232bfc8@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=db56459ea4ac4a676ae4b4678f633e55da005a9b Signed-off-by: Theodore Ts'o

unicode: clean up the Kconfig symbol confusion

2022-01-21T00:57:24+00:00

Turn the CONFIG_UNICODE symbol into a tristate that generates some always built in code and remove the confusing CONFIG_UNICODE_UTF8_DATA symbol. Note that a lot of the IS_ENABLED() checks could be turned from cpp statements into normal ifs, but this change is intended to be fairly mechanic, so that should be cleaned up later. Fixes: 2b3d04787012 ("unicode: Add utf8-data module") Reported-by: Linus Torvalds Reviewed-by: Eric Biggers Signed-off-by: Christoph Hellwig Signed-off-by: Gabriel Krisman Bertazi

ext4: handle casefolding with encryption

2021-04-06T02:04:20+00:00

This adds support for encryption with casefolding. Since the name on disk is case preserving, and also encrypted, we can no longer just recompute the hash on the fly. Additionally, to avoid leaking extra information from the hash of the unencrypted name, we use siphash via an fscrypt v2 policy. The hash is stored at the end of the directory entry for all entries inside of an encrypted and casefolded directory apart from those that deal with '.' and '..'. This way, the change is backwards compatible with existing ext4 filesystems. [ Changed to advertise this feature via the file: /sys/fs/ext4/features/encrypted_casefold -- TYT ] Signed-off-by: Daniel Rosenberg Reviewed-by: Andreas Dilger Link: https://lore.kernel.org/r/20210319073414.1381041-2-drosen@google.com Signed-off-by: Theodore Ts'o

ext4: use generic casefolding support

2020-10-28T17:43:13+00:00

This switches ext4 over to the generic support provided in libfs. Since casefolded dentries behave the same in ext4 and f2fs, we decrease the maintenance burden by unifying them, and any optimizations will immediately apply to both. Signed-off-by: Daniel Rosenberg Reviewed-by: Eric Biggers Link: https://lore.kernel.org/r/20201028050820.1636571-1-drosen@google.com Signed-off-by: Theodore Ts'o

ext4: change to use fallthrough macro

2020-08-18T18:27:40+00:00

Change to use fallthrough macro in switch case. Signed-off-by: Shijie Luo Reviewed-by: Ritesh Harjani Link: https://lore.kernel.org/r/20200810114435.24182-1-luoshijie1@huawei.com Signed-off-by: Theodore Ts'o

ext4: fix kernel oops caused by spurious casefold flag

2019-09-03T05:43:17+00:00

If an directory has the a casefold flag set without the casefold feature set, s_encoding will not be initialized, and this will cause the kernel to dereference a NULL pointer. In addition to adding checks to avoid these kernel oops, attempts to load inodes with the casefold flag when the casefold feature is not enable will cause the file system to be declared corrupted. Signed-off-by: Theodore Ts'o

ext4: Support case-insensitive file name lookups

2019-04-25T18:12:08+00:00

This patch implements the actual support for case-insensitive file name lookups in ext4, based on the feature bit and the encoding stored in the superblock. A filesystem that has the casefold feature set is able to configure directories with the +F (EXT4_CASEFOLD_FL) attribute, enabling lookups to succeed in that directory in a case-insensitive fashion, i.e: match a directory entry even if the name used by userspace is not a byte per byte match with the disk name, but is an equivalent case-insensitive version of the Unicode string. This operation is called a case-insensitive file name lookup. The feature is configured as an inode attribute applied to directories and inherited by its children. This attribute can only be enabled on empty directories for filesystems that support the encoding feature, thus preventing collision of file names that only differ by case. * dcache handling: For a +F directory, Ext4 only stores the first equivalent name dentry used in the dcache. This is done to prevent unintentional duplication of dentries in the dcache, while also allowing the VFS code to quickly find the right entry in the cache despite which equivalent string was used in a previous lookup, without having to resort to ->lookup(). d_hash() of casefolded directories is implemented as the hash of the casefolded string, such that we always have a well-known bucket for all the equivalencies of the same string. d_compare() uses the utf8_strncasecmp() infrastructure, which handles the comparison of equivalent, same case, names as well. For now, negative lookups are not inserted in the dcache, since they would need to be invalidated anyway, because we can't trust missing file dentries. This is bad for performance but requires some leveraging of the vfs layer to fix. We can live without that for now, and so does everyone else. * on-disk data: Despite using a specific version of the name as the internal representation within the dcache, the name stored and fetched from the disk is a byte-per-byte match with what the user requested, making this implementation 'name-preserving'. i.e. no actual information is lost when writing to storage. DX is supported by modifying the hashes used in +F directories to make them case/encoding-aware. The new disk hashes are calculated as the hash of the full casefolded string, instead of the string directly. This allows us to efficiently search for file names in the htree without requiring the user to provide an exact name. * Dealing with invalid sequences: By default, when a invalid UTF-8 sequence is identified, ext4 will treat it as an opaque byte sequence, ignoring the encoding and reverting to the old behavior for that unique file. This means that case-insensitive file name lookup will not work only for that file. An optional bit can be set in the superblock telling the filesystem code and userspace tools to enforce the encoding. When that optional bit is set, any attempt to create a file name using an invalid UTF-8 sequence will fail and return an error to userspace. * Normalization algorithm: The UTF-8 algorithms used to compare strings in ext4 is implemented lives in fs/unicode, and is based on a previous version developed by SGI. It implements the Canonical decomposition (NFD) algorithm described by the Unicode specification 12.1, or higher, combined with the elimination of ignorable code points (NFDi) and full case-folding (CF) as documented in fs/unicode/utf8_norm.c. NFD seems to be the best normalization method for EXT4 because: - It has a lower cost than NFC/NFKC (which requires decomposing to NFD as an intermediary step) - It doesn't eliminate important semantic meaning like compatibility decompositions. Although: - This implementation is not completely linguistic accurate, because different languages have conflicting rules, which would require the specialization of the filesystem to a given locale, which brings all sorts of problems for removable media and for users who use more than one language. Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Theodore Ts'o

ext4: annotate implicit fall throughs

2019-02-21T15:49:53+00:00

There is a plan to build the kernel with -Wimplicit-fallthrough and these places in the code produced warnings (W=1). Fix them up. This commit remove the following warnings: fs/ext4/hash.c:233:15: warning: this statement may fall through [-Wimplicit-fallthrough=] fs/ext4/hash.c:246:15: warning: this statement may fall through [-Wimplicit-fallthrough=] Signed-off-by: Mathieu Malaterre Signed-off-by: Theodore Ts'o Reviewed-by: Andreas Dilger

ext4: fix up remaining files with SPDX cleanups

2017-12-18T03:00:59+00:00

A number of ext4 source files were skipped due because their copyright permission statements didn't match the expected text used by the automated conversion utilities. I've added SPDX tags for the rest. While looking at some of these files, I've noticed that we have quite a bit of variation on the licenses that were used --- in particular some of the Red Hat licenses on the jbd2 files use a GPL2+ license, and we have some files that have a LGPL-2.1 license (which was quite surprising). I've not attempted to do any license changes. Even if it is perfectly legal to relicense to GPL 2.0-only for consistency's sake, that should be done with ext4 developer community discussion. Signed-off-by: Theodore Ts'o