From 6c9468aad215a198742c8375b0415e42521c905c Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 10 Aug 2025 00:56:54 -0700 Subject: fscrypt: replace raw loads of info pointer with helper function Add and use a helper function fscrypt_get_inode_info_raw(). It loads an inode's fscrypt info pointer using a raw dereference, which is appropriate when the caller knows the key setup already happened. This eliminates most occurrences of inode::i_crypt_info in the source, in preparation for replacing that with a filesystem-specific field. Co-developed-by: Christian Brauner Signed-off-by: Eric Biggers Link: https://lore.kernel.org/20250810075706.172910-2-ebiggers@kernel.org Signed-off-by: Christian Brauner --- include/linux/fscrypt.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux/fscrypt.h') diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 10dd161690a2..23c5198612d1 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -195,6 +195,22 @@ struct fscrypt_operations { int fscrypt_d_revalidate(struct inode *dir, const struct qstr *name, struct dentry *dentry, unsigned int flags); +/* + * Load the inode's fscrypt info pointer, using a raw dereference. Since this + * uses a raw dereference with no memory barrier, it is appropriate to use only + * when the caller knows the inode's key setup already happened, resulting in + * non-NULL fscrypt info. E.g., the file contents en/decryption functions use + * this, since fscrypt_file_open() set up the key. + */ +static inline struct fscrypt_inode_info * +fscrypt_get_inode_info_raw(const struct inode *inode) +{ + struct fscrypt_inode_info *ci = inode->i_crypt_info; + + VFS_WARN_ON_ONCE(ci == NULL); + return ci; +} + static inline struct fscrypt_inode_info * fscrypt_get_inode_info(const struct inode *inode) { -- cgit v1.2.3 From 93221de31a8df6710e02328f82dc68d7ab4ad9e6 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 10 Aug 2025 00:56:55 -0700 Subject: fscrypt: add support for info in fs-specific part of inode Add an inode_info_offs field to struct fscrypt_operations, and update fs/crypto/ to support it. When set to a nonzero value, it specifies the offset to the fscrypt_inode_info pointer within the filesystem-specific part of the inode structure, to be used instead of inode::i_crypt_info. Since this makes inode::i_crypt_info no longer necessarily used, update comments that mentioned it. This is a prerequisite for a later commit that removes inode::i_crypt_info, saving memory and improving cache efficiency with filesystems that don't support fscrypt. Co-developed-by: Christian Brauner Signed-off-by: Eric Biggers Link: https://lore.kernel.org/20250810075706.172910-3-ebiggers@kernel.org Signed-off-by: Christian Brauner --- include/linux/fscrypt.h | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'include/linux/fscrypt.h') diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 23c5198612d1..d7ff53accbfe 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -61,6 +61,12 @@ struct fscrypt_name { /* Crypto operations for filesystems */ struct fscrypt_operations { + /* + * The offset of the pointer to struct fscrypt_inode_info in the + * filesystem-specific part of the inode, relative to the beginning of + * the common part of the inode (the 'struct inode'). + */ + ptrdiff_t inode_info_offs; /* * If set, then fs/crypto/ will allocate a global bounce page pool the @@ -195,6 +201,14 @@ struct fscrypt_operations { int fscrypt_d_revalidate(struct inode *dir, const struct qstr *name, struct dentry *dentry, unsigned int flags); +static inline struct fscrypt_inode_info ** +fscrypt_inode_info_addr(const struct inode *inode) +{ + if (inode->i_sb->s_cop->inode_info_offs == 0) + return (struct fscrypt_inode_info **)&inode->i_crypt_info; + return (void *)inode + inode->i_sb->s_cop->inode_info_offs; +} + /* * Load the inode's fscrypt info pointer, using a raw dereference. Since this * uses a raw dereference with no memory barrier, it is appropriate to use only @@ -205,7 +219,7 @@ int fscrypt_d_revalidate(struct inode *dir, const struct qstr *name, static inline struct fscrypt_inode_info * fscrypt_get_inode_info_raw(const struct inode *inode) { - struct fscrypt_inode_info *ci = inode->i_crypt_info; + struct fscrypt_inode_info *ci = *fscrypt_inode_info_addr(inode); VFS_WARN_ON_ONCE(ci == NULL); return ci; @@ -216,11 +230,11 @@ fscrypt_get_inode_info(const struct inode *inode) { /* * Pairs with the cmpxchg_release() in fscrypt_setup_encryption_info(). - * I.e., another task may publish ->i_crypt_info concurrently, executing - * a RELEASE barrier. We need to use smp_load_acquire() here to safely + * I.e., another task may publish the fscrypt info concurrently, + * executing a RELEASE barrier. Use smp_load_acquire() here to safely * ACQUIRE the memory the other task published. */ - return smp_load_acquire(&inode->i_crypt_info); + return smp_load_acquire(fscrypt_inode_info_addr(inode)); } /** -- cgit v1.2.3 From ab90c2d2476c4dd6deddd089c7e83b858d135783 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 10 Aug 2025 00:57:00 -0700 Subject: fs: remove inode::i_crypt_info Now that all fscrypt-capable filesystems store the pointer to fscrypt_inode_info in the filesystem-specific part of the inode structure, inode::i_crypt_info is no longer needed. Update fscrypt_inode_info_addr() to no longer support the fallback to inode::i_crypt_info. Finally, remove inode::i_crypt_info itself along with the now-unnecessary forward declaration of fscrypt_inode_info. The end result of the migration to the filesystem-specific pointer is memory savings on CONFIG_FS_ENCRYPTION=y kernels for all filesystems that don't support fscrypt. Specifically, their in-memory inodes are now smaller by the size of a pointer: either 4 or 8 bytes. Co-developed-by: Christian Brauner Signed-off-by: Eric Biggers Link: https://lore.kernel.org/20250810075706.172910-8-ebiggers@kernel.org Signed-off-by: Christian Brauner --- include/linux/fscrypt.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'include/linux/fscrypt.h') diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index d7ff53accbfe..516aba5b858b 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -201,11 +201,15 @@ struct fscrypt_operations { int fscrypt_d_revalidate(struct inode *dir, const struct qstr *name, struct dentry *dentry, unsigned int flags); +/* + * Returns the address of the fscrypt info pointer within the + * filesystem-specific part of the inode. (To save memory on filesystems that + * don't support fscrypt, a field in 'struct inode' itself is no longer used.) + */ static inline struct fscrypt_inode_info ** fscrypt_inode_info_addr(const struct inode *inode) { - if (inode->i_sb->s_cop->inode_info_offs == 0) - return (struct fscrypt_inode_info **)&inode->i_crypt_info; + VFS_WARN_ON_ONCE(inode->i_sb->s_cop->inode_info_offs == 0); return (void *)inode + inode->i_sb->s_cop->inode_info_offs; } -- cgit v1.2.3