f2fs: refactor read path to allow multiple postprocessing steps

Currently f2fs's ->readpage() and ->readpages() assume that either the
data undergoes no postprocessing, or decryption only.  But with
fs-verity, there will be an additional authenticity verification step,
and it may be needed either by itself, or combined with decryption.

To support this, store a 'struct bio_post_read_ctx' in ->bi_private
which contains a work struct, a bitmask of postprocessing steps that are
enabled, and an indicator of the current step.  The bio completion
routine, if there was no I/O error, enqueues the first postprocessing
step.  When that completes, it continues to the next step.  Pages that
fail any postprocessing step have PageError set.  Once all steps have
completed, pages without PageError set are set Uptodate, and all pages
are unlocked.

Also replace f2fs_encrypted_file() with a new function
f2fs_post_read_required() in places like direct I/O and garbage
collection that really should be testing whether the file needs special
I/O processing, not whether it is encrypted specifically.

This may also be useful for other future f2fs features such as
compression.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1df7f10..ea92c18 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2858,6 +2858,8 @@ void destroy_checkpoint_caches(void);
 /*
  * data.c
  */
+int f2fs_init_post_read_processing(void);
+void f2fs_destroy_post_read_processing(void);
 void f2fs_submit_merged_write(struct f2fs_sb_info *sbi, enum page_type type);
 void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
 				struct inode *inode, nid_t ino, pgoff_t idx,
@@ -3218,9 +3220,13 @@ static inline void f2fs_set_encrypted_inode(struct inode *inode)
 #endif
 }
 
-static inline bool f2fs_bio_encrypted(struct bio *bio)
+/*
+ * Returns true if the reads of the inode's data need to undergo some
+ * postprocessing step, like decryption or authenticity verification.
+ */
+static inline bool f2fs_post_read_required(struct inode *inode)
 {
-	return bio->bi_private != NULL;
+	return f2fs_encrypted_file(inode);
 }
 
 #define F2FS_FEATURE_FUNCS(name, flagname) \
@@ -3288,7 +3294,7 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
 
 static inline bool f2fs_force_buffered_io(struct inode *inode, int rw)
 {
-	return (f2fs_encrypted_file(inode) ||
+	return (f2fs_post_read_required(inode) ||
 			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
 			F2FS_I_SB(inode)->s_ndevs);
 }