ext4: Further de-generalize the bio postprocessing code

Since the bio postprocessing code in fs/ext4/readpage.c is now used only
for fsverity, rename things accordingly.

Also:

- Don't create the caches at all when !CONFIG_FS_VERITY.
- Remove the unused inode argument from ext4_set_verity_work().

Link: https://patch.msgid.link/20260713023708.9245-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

3 files changed, 36 insertions, 39 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 920a8ec1b948..489ed6dcee52 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3829,8 +3829,8 @@ static inline void ext4_set_de_type(struct super_block *sb,
 /* readpages.c */
 int ext4_read_folio(struct file *file, struct folio *folio);
 void ext4_readahead(struct readahead_control *rac);
-extern int __init ext4_init_post_read_processing(void);
-extern void ext4_exit_post_read_processing(void);
+int __init ext4_init_verity_caches(void);
+void ext4_exit_verity_caches(void);
 
 /* symlink.c */
 extern const struct inode_operations ext4_encrypted_symlink_inode_operations;
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 8af183798a33..c7b6cdb2e124 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -47,12 +47,12 @@
 #include "ext4.h"
 #include <trace/events/ext4.h>
 
-#define NUM_PREALLOC_POST_READ_CTXS	128
+#define NUM_VERITY_WORKS 128
 
-static struct kmem_cache *bio_post_read_ctx_cache;
-static mempool_t *bio_post_read_ctx_pool;
+static struct kmem_cache *ext4_verity_work_cache;
+static mempool_t *ext4_verity_work_pool;
 
-struct bio_post_read_ctx {
+struct ext4_verity_work {
 	struct bio *bio;
 	struct fsverity_info *vi;
 	struct work_struct work;
@@ -65,22 +65,22 @@ static void __read_end_io(struct bio *bio)
 	bio_for_each_folio_all(fi, bio)
 		folio_end_read(fi.folio, bio->bi_status == 0);
 	if (bio->bi_private)
-		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
+		mempool_free(bio->bi_private, ext4_verity_work_pool);
 	bio_put(bio);
 }
 
 static void verity_work(struct work_struct *work)
 {
-	struct bio_post_read_ctx *ctx =
-		container_of(work, struct bio_post_read_ctx, work);
+	struct ext4_verity_work *ctx =
+		container_of(work, struct ext4_verity_work, work);
 	struct bio *bio = ctx->bio;
 	struct fsverity_info *vi = ctx->vi;
 
 	/*
-	 * Free the bio_post_read_ctx right away, since it's no longer needed.
+	 * Free the ext4_verity_work right away, since it's no longer needed.
 	 * This relieves the pressure on the mempool as much as possible.
 	 */
-	mempool_free(ctx, bio_post_read_ctx_pool);
+	mempool_free(ctx, ext4_verity_work_pool);
 	bio->bi_private = NULL;
 
 	fsverity_verify_bio(vi, bio);
@@ -88,12 +88,6 @@ static void verity_work(struct work_struct *work)
 	__read_end_io(bio);
 }
 
-static bool bio_post_read_required(struct bio *bio)
-{
-	return IS_ENABLED(CONFIG_FS_VERITY) && bio->bi_private &&
-	       !bio->bi_status;
-}
-
 /*
  * I/O completion handler for multipage BIOs.
  *
@@ -108,8 +102,9 @@ static bool bio_post_read_required(struct bio *bio)
  */
 static void mpage_end_io(struct bio *bio)
 {
-	if (bio_post_read_required(bio)) {
-		struct bio_post_read_ctx *ctx = bio->bi_private;
+	if (IS_ENABLED(CONFIG_FS_VERITY) && bio->bi_private &&
+	    !bio->bi_status) {
+		struct ext4_verity_work *ctx = bio->bi_private;
 
 		INIT_WORK(&ctx->work, verity_work);
 		fsverity_enqueue_verify_work(&ctx->work);
@@ -118,14 +113,12 @@ static void mpage_end_io(struct bio *bio)
 	__read_end_io(bio);
 }
 
-static void ext4_set_bio_post_read_ctx(struct bio *bio,
-				       const struct inode *inode,
-				       struct fsverity_info *vi)
+static void ext4_set_verity_work(struct bio *bio, struct fsverity_info *vi)
 {
 	if (vi) {
 		/* Due to the mempool, this never fails. */
-		struct bio_post_read_ctx *ctx =
-			mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
+		struct ext4_verity_work *ctx =
+			mempool_alloc(ext4_verity_work_pool, GFP_NOFS);
 
 		ctx->bio = bio;
 		ctx->vi = vi;
@@ -289,7 +282,7 @@ static int ext4_mpage_readpages(struct inode *inode, struct fsverity_info *vi,
 			bio = bio_alloc(bdev, bio_max_segs(nr_pages),
 					REQ_OP_READ, GFP_KERNEL);
 			fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_KERNEL);
-			ext4_set_bio_post_read_ctx(bio, inode, vi);
+			ext4_set_verity_work(bio, vi);
 			bio->bi_iter.bi_sector = first_block << (blkbits - 9);
 			bio->bi_end_io = mpage_end_io;
 			if (rac)
@@ -363,27 +356,31 @@ void ext4_readahead(struct readahead_control *rac)
 	ext4_mpage_readpages(inode, vi, rac, NULL);
 }
 
-int __init ext4_init_post_read_processing(void)
+int __init ext4_init_verity_caches(void)
 {
-	bio_post_read_ctx_cache = KMEM_CACHE(bio_post_read_ctx, SLAB_RECLAIM_ACCOUNT);
+	if (!IS_ENABLED(CONFIG_FS_VERITY))
+		return 0;
+	ext4_verity_work_cache =
+		KMEM_CACHE(ext4_verity_work, SLAB_RECLAIM_ACCOUNT);
 
-	if (!bio_post_read_ctx_cache)
+	if (!ext4_verity_work_cache)
 		goto fail;
-	bio_post_read_ctx_pool =
-		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
-					 bio_post_read_ctx_cache);
-	if (!bio_post_read_ctx_pool)
+	ext4_verity_work_pool = mempool_create_slab_pool(
+		NUM_VERITY_WORKS, ext4_verity_work_cache);
+	if (!ext4_verity_work_pool)
 		goto fail_free_cache;
 	return 0;
 
 fail_free_cache:
-	kmem_cache_destroy(bio_post_read_ctx_cache);
+	kmem_cache_destroy(ext4_verity_work_cache);
 fail:
 	return -ENOMEM;
 }
 
-void ext4_exit_post_read_processing(void)
+void ext4_exit_verity_caches(void)
 {
-	mempool_destroy(bio_post_read_ctx_pool);
-	kmem_cache_destroy(bio_post_read_ctx_cache);
+	if (!IS_ENABLED(CONFIG_FS_VERITY))
+		return;
+	mempool_destroy(ext4_verity_work_pool);
+	kmem_cache_destroy(ext4_verity_work_cache);
 }
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 245f67d10ded..cb9ca0dc4664 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -7531,7 +7531,7 @@ static int __init ext4_init_fs(void)
 	if (err)
 		goto out7;
 
-	err = ext4_init_post_read_processing();
+	err = ext4_init_verity_caches();
 	if (err)
 		goto out6;
 
@@ -7580,7 +7580,7 @@ out3:
 out4:
 	ext4_exit_pageio();
 out5:
-	ext4_exit_post_read_processing();
+	ext4_exit_verity_caches();
 out6:
 	ext4_exit_pending();
 out7:
@@ -7601,7 +7601,7 @@ static void __exit ext4_exit_fs(void)
 	ext4_exit_sysfs();
 	ext4_exit_system_zone();
 	ext4_exit_pageio();
-	ext4_exit_post_read_processing();
+	ext4_exit_verity_caches();
 	ext4_exit_es();
 	ext4_exit_pending();
 }