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fscrypt: simplify bounce page handling

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Currently, bounce page handling for writes to encrypted files is
unnecessarily complicated.  A fscrypt_ctx is allocated along with each
bounce page, page_private(bounce_page) points to this fscrypt_ctx, and
fscrypt_ctx::w::control_page points to the original pagecache page.

However, because writes don't use the fscrypt_ctx for anything else,
there's no reason why page_private(bounce_page) can't just point to the
original pagecache page directly.

Therefore, this patch makes this change.  In the process, it also cleans
up the API exposed to filesystems that allows testing whether a page is
a bounce page, getting the pagecache page from a bounce page, and
freeing a bounce page.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
2019-05-20 09:29:39 -07:00
parent cd6c84d8f0
commit d2d0727b16
6 changed files with 84 additions and 148 deletions
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38
include/linux/fscrypt.h
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@@ -112,12 +112,17 @@ extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
unsigned int, u64);
static inline struct page *fscrypt_control_page(struct page *page)
static inline bool fscrypt_is_bounce_page(struct page *page)
{
return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
return page->mapping == NULL;
}
extern void fscrypt_restore_control_page(struct page *);
static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
{
return (struct page *)page_private(bounce_page);
}
extern void fscrypt_free_bounce_page(struct page *bounce_page);
/* policy.c */
extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
@@ -223,7 +228,6 @@ static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
extern void fscrypt_decrypt_bio(struct bio *);
extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
struct bio *bio);
extern void fscrypt_pullback_bio_page(struct page **, bool);
extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
unsigned int);
@@ -300,15 +304,19 @@ static inline int fscrypt_decrypt_page(const struct inode *inode,
return -EOPNOTSUPP;
}
static inline struct page *fscrypt_control_page(struct page *page)
static inline bool fscrypt_is_bounce_page(struct page *page)
{
return false;
}
static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
{
WARN_ON_ONCE(1);
return ERR_PTR(-EINVAL);
}
static inline void fscrypt_restore_control_page(struct page *page)
static inline void fscrypt_free_bounce_page(struct page *bounce_page)
{
return;
}
/* policy.c */
@@ -410,11 +418,6 @@ static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
{
}
static inline void fscrypt_pullback_bio_page(struct page **page, bool restore)
{
return;
}
static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
sector_t pblk, unsigned int len)
{
@@ -692,4 +695,15 @@ static inline int fscrypt_encrypt_symlink(struct inode *inode,
return 0;
}
/* If *pagep is a bounce page, free it and set *pagep to the pagecache page */
static inline void fscrypt_finalize_bounce_page(struct page **pagep)
{
struct page *page = *pagep;
if (fscrypt_is_bounce_page(page)) {
*pagep = fscrypt_pagecache_page(page);
fscrypt_free_bounce_page(page);
}
}
#endif /* _LINUX_FSCRYPT_H */