fs,block: yield devices early

Currently a device is only really released once the umount returns to
userspace due to how file closing works. That ultimately could cause
an old umount assumption to be violated that concurrent umount and mount
don't fail. So an exclusively held device with a temporary holder should
be yielded before the filesystem is gone. Add a helper that allows
callers to do that. This also allows us to remove the two holder ops
that Linus wasn't excited about.

Link: https://lore.kernel.org/r/20240326-vfs-bdev-end_holder-v1-1-20af85202918@kernel.org
Fixes: f3a608827d1f ("bdev: open block device as files") # mainline only
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

10 files changed, 18 insertions, 36 deletions

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index ad28e370b640..cb7b4de11a49 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -143,7 +143,7 @@ void bch2_free_super(struct bch_sb_handle *sb)
 {
 	kfree(sb->bio);
 	if (!IS_ERR_OR_NULL(sb->s_bdev_file))
-		fput(sb->s_bdev_file);
+		bdev_fput(sb->s_bdev_file);
 	kfree(sb->holder);
 	kfree(sb->sb_name);
 
diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 39e75131fd5a..9901057a15ba 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -495,7 +495,7 @@ static void cramfs_kill_sb(struct super_block *sb)
 		sb->s_mtd = NULL;
 	} else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
 		sync_blockdev(sb->s_bdev);
-		fput(sb->s_bdev_file);
+		bdev_fput(sb->s_bdev_file);
 	}
 	kfree(sbi);
 }
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cfb8449c731f..044135796f2b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5668,7 +5668,7 @@ failed_mount:
 	brelse(sbi->s_sbh);
 	if (sbi->s_journal_bdev_file) {
 		invalidate_bdev(file_bdev(sbi->s_journal_bdev_file));
-		fput(sbi->s_journal_bdev_file);
+		bdev_fput(sbi->s_journal_bdev_file);
 	}
 out_fail:
 	invalidate_bdev(sb->s_bdev);
@@ -5913,7 +5913,7 @@ static struct file *ext4_get_journal_blkdev(struct super_block *sb,
 out_bh:
 	brelse(bh);
 out_bdev:
-	fput(bdev_file);
+	bdev_fput(bdev_file);
 	return ERR_PTR(errno);
 }
 
@@ -5952,7 +5952,7 @@ static journal_t *ext4_open_dev_journal(struct super_block *sb,
 out_journal:
 	jbd2_journal_destroy(journal);
 out_bdev:
-	fput(bdev_file);
+	bdev_fput(bdev_file);
 	return ERR_PTR(errno);
 }
 
@@ -7327,7 +7327,7 @@ static void ext4_kill_sb(struct super_block *sb)
 	kill_block_super(sb);
 
 	if (bdev_file)
-		fput(bdev_file);
+		bdev_fput(bdev_file);
 }
 
 static struct file_system_type ext4_fs_type = {
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index a6867f26f141..a4bc26dfdb1a 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1558,7 +1558,7 @@ static void destroy_device_list(struct f2fs_sb_info *sbi)
 
 	for (i = 0; i < sbi->s_ndevs; i++) {
 		if (i > 0)
-			fput(FDEV(i).bdev_file);
+			bdev_fput(FDEV(i).bdev_file);
 #ifdef CONFIG_BLK_DEV_ZONED
 		kvfree(FDEV(i).blkz_seq);
 #endif
diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 73389c68e251..9609349e92e5 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1141,7 +1141,7 @@ journal_found:
 	lbmLogShutdown(log);
 
       close:		/* close external log device */
-	fput(bdev_file);
+	bdev_fput(bdev_file);
 
       free:		/* free log descriptor */
 	mutex_unlock(&jfs_log_mutex);
@@ -1485,7 +1485,7 @@ int lmLogClose(struct super_block *sb)
 	bdev_file = log->bdev_file;
 	rc = lmLogShutdown(log);
 
-	fput(bdev_file);
+	bdev_fput(bdev_file);
 
 	kfree(log);
 
diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index 6474529c4253..e539ccd39e1e 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -2589,7 +2589,7 @@ static void journal_list_init(struct super_block *sb)
 static void release_journal_dev(struct reiserfs_journal *journal)
 {
 	if (journal->j_bdev_file) {
-		fput(journal->j_bdev_file);
+		bdev_fput(journal->j_bdev_file);
 		journal->j_bdev_file = NULL;
 	}
 }
diff --git a/fs/romfs/super.c b/fs/romfs/super.c
index 2be227532f39..2cbb92462074 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -594,7 +594,7 @@ static void romfs_kill_sb(struct super_block *sb)
 #ifdef CONFIG_ROMFS_ON_BLOCK
 	if (sb->s_bdev) {
 		sync_blockdev(sb->s_bdev);
-		fput(sb->s_bdev_file);
+		bdev_fput(sb->s_bdev_file);
 	}
 #endif
 }
diff --git a/fs/super.c b/fs/super.c
index 71d9779c42b1..69ce6c600968 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1515,29 +1515,11 @@ static int fs_bdev_thaw(struct block_device *bdev)
 	return error;
 }
 
-static void fs_bdev_super_get(void *data)
-{
-	struct super_block *sb = data;
-
-	spin_lock(&sb_lock);
-	sb->s_count++;
-	spin_unlock(&sb_lock);
-}
-
-static void fs_bdev_super_put(void *data)
-{
-	struct super_block *sb = data;
-
-	put_super(sb);
-}
-
 const struct blk_holder_ops fs_holder_ops = {
 	.mark_dead		= fs_bdev_mark_dead,
 	.sync			= fs_bdev_sync,
 	.freeze			= fs_bdev_freeze,
 	.thaw			= fs_bdev_thaw,
-	.get_holder		= fs_bdev_super_get,
-	.put_holder		= fs_bdev_super_put,
 };
 EXPORT_SYMBOL_GPL(fs_holder_ops);
 
@@ -1562,7 +1544,7 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 	 * writable from userspace even for a read-only block device.
 	 */
 	if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
-		fput(bdev_file);
+		bdev_fput(bdev_file);
 		return -EACCES;
 	}
 
@@ -1573,7 +1555,7 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 	if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {
 		if (fc)
 			warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
-		fput(bdev_file);
+		bdev_fput(bdev_file);
 		return -EBUSY;
 	}
 	spin_lock(&sb_lock);
@@ -1693,7 +1675,7 @@ void kill_block_super(struct super_block *sb)
 	generic_shutdown_super(sb);
 	if (bdev) {
 		sync_blockdev(bdev);
-		fput(sb->s_bdev_file);
+		bdev_fput(sb->s_bdev_file);
 	}
 }
 
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 1a18c381127e..f0fa02264eda 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -2030,7 +2030,7 @@ xfs_free_buftarg(
 	fs_put_dax(btp->bt_daxdev, btp->bt_mount);
 	/* the main block device is closed by kill_block_super */
 	if (btp->bt_bdev != btp->bt_mount->m_super->s_bdev)
-		fput(btp->bt_bdev_file);
+		bdev_fput(btp->bt_bdev_file);
 	kfree(btp);
 }
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index c21f10ab0f5d..bce020374c5e 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -485,7 +485,7 @@ xfs_open_devices(
 		mp->m_logdev_targp = mp->m_ddev_targp;
 		/* Handle won't be used, drop it */
 		if (logdev_file)
-			fput(logdev_file);
+			bdev_fput(logdev_file);
 	}
 
 	return 0;
@@ -497,10 +497,10 @@ xfs_open_devices(
 	xfs_free_buftarg(mp->m_ddev_targp);
  out_close_rtdev:
 	 if (rtdev_file)
-		fput(rtdev_file);
+		bdev_fput(rtdev_file);
  out_close_logdev:
 	if (logdev_file)
-		fput(logdev_file);
+		bdev_fput(logdev_file);
 	return error;
 }