Commit 608af703 authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Jaegeuk Kim
Browse files

libfs: Add generic function for setting dentry_ops 



This adds a function to set dentry operations at lookup time that will
work for both encrypted filenames and casefolded filenames.

A filesystem that supports both features simultaneously can use this
function during lookup preparations to set up its dentry operations once
fscrypt no longer does that itself.

Currently the casefolding dentry operation are always set if the
filesystem defines an encoding because the features is toggleable on
empty directories. Unlike in the encryption case, the dentry operations
used come from the parent. Since we don't know what set of functions
we'll eventually need, and cannot change them later, we enable the
casefolding operations if the filesystem supports them at all.

By splitting out the various cases, we support as few dentry operations
as we can get away with, maximizing compatibility with overlayfs, which
will not function if a filesystem supports certain dentry_operations.

Signed-off-by: default avatarDaniel Rosenberg <drosen@google.com>
Reviewed-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent beb78181

fs/libfs.c

+70 −0
Original line number Diff line number Diff line
@@ -1449,4 +1449,74 @@ int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str) 
	return 0;

}

EXPORT_SYMBOL(generic_ci_d_hash);



static const struct dentry_operations generic_ci_dentry_ops = {

	.d_hash = generic_ci_d_hash,

	.d_compare = generic_ci_d_compare,

};

#endif



#ifdef CONFIG_FS_ENCRYPTION

static const struct dentry_operations generic_encrypted_dentry_ops = {

	.d_revalidate = fscrypt_d_revalidate,

};

#endif



#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)

static const struct dentry_operations generic_encrypted_ci_dentry_ops = {

	.d_hash = generic_ci_d_hash,

	.d_compare = generic_ci_d_compare,

	.d_revalidate = fscrypt_d_revalidate,

};

#endif



/**

 * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry

 * @dentry:	dentry to set ops on

 *

 * Casefolded directories need d_hash and d_compare set, so that the dentries

 * contained in them are handled case-insensitively.  Note that these operations

 * are needed on the parent directory rather than on the dentries in it, and

 * while the casefolding flag can be toggled on and off on an empty directory,

 * dentry_operations can't be changed later.  As a result, if the filesystem has

 * casefolding support enabled at all, we have to give all dentries the

 * casefolding operations even if their inode doesn't have the casefolding flag

 * currently (and thus the casefolding ops would be no-ops for now).

 *

 * Encryption works differently in that the only dentry operation it needs is

 * d_revalidate, which it only needs on dentries that have the no-key name flag.

 * The no-key flag can't be set "later", so we don't have to worry about that.

 *

 * Finally, to maximize compatibility with overlayfs (which isn't compatible

 * with certain dentry operations) and to avoid taking an unnecessary

 * performance hit, we use custom dentry_operations for each possible

 * combination rather than always installing all operations.

 */

void generic_set_encrypted_ci_d_ops(struct dentry *dentry)

{

#ifdef CONFIG_FS_ENCRYPTION

	bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;

#endif

#ifdef CONFIG_UNICODE

	bool needs_ci_ops = dentry->d_sb->s_encoding;

#endif

#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)

	if (needs_encrypt_ops && needs_ci_ops) {

		d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);

		return;

	}

#endif

#ifdef CONFIG_FS_ENCRYPTION

	if (needs_encrypt_ops) {

		d_set_d_op(dentry, &generic_encrypted_dentry_ops);

		return;

	}

#endif

#ifdef CONFIG_UNICODE

	if (needs_ci_ops) {

		d_set_d_op(dentry, &generic_ci_dentry_ops);

		return;

	}

#endif

}

EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -3186,6 +3186,7 @@ extern int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str); 
extern int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,

				const char *str, const struct qstr *name);

#endif

extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);



#ifdef CONFIG_MIGRATION

extern int buffer_migrate_page(struct address_space *,

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