exfat: Implement sops->shutdown and ioctl

We found that when writing a large file through buffer write, if the
disk is inaccessible, exFAT does not return an error normally, which
leads to the writing process not stopping properly.

To easily reproduce this issue, you can follow the steps below:

1. format a device to exFAT and then mount (with a full disk erase)
2. dd if=/dev/zero of=/exfat_mount/test.img bs=1M count=8192
3. eject the device

You may find that the dd process does not stop immediately and may
continue for a long time.

The root cause of this issue is that during buffer write process,
exFAT does not need to access the disk to look up directory entries
or the FAT table (whereas FAT would do) every time data is written.
Instead, exFAT simply marks the buffer as dirty and returns,
delegating the writeback operation to the writeback process.

If the disk cannot be accessed at this time, the error will only be
returned to the writeback process, and the original process will not
receive the error, so it cannot be returned to the user side.

When the disk cannot be accessed normally, an error should be returned
to stop the writing process.

Implement sops->shutdown and ioctl to shut down the file system
when underlying block device is marked dead.

Signed-off-by: Dongliang Cui <dongliang.cui@unisoc.com>
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 5be214288a05..3cdc1de362a9 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -10,6 +10,7 @@
 #include <linux/ratelimit.h>
 #include <linux/nls.h>
 #include <linux/blkdev.h>
+#include <uapi/linux/exfat.h>
 
 #define EXFAT_ROOT_INO		1
 
@@ -148,6 +149,9 @@ enum {
 #define DIR_CACHE_SIZE		\
 	(DIV_ROUND_UP(EXFAT_DEN_TO_B(ES_MAX_ENTRY_NUM), SECTOR_SIZE) + 1)
 
+/* Superblock flags */
+#define EXFAT_FLAGS_SHUTDOWN	1
+
 struct exfat_dentry_namebuf {
 	char *lfn;
 	int lfnbuf_len; /* usually MAX_UNINAME_BUF_SIZE */
@@ -267,6 +271,8 @@ struct exfat_sb_info {
 	unsigned int clu_srch_ptr; /* cluster search pointer */
 	unsigned int used_clusters; /* number of used clusters */
 
+	unsigned long s_exfat_flags; /* Exfat superblock flags */
+
 	struct mutex s_lock; /* superblock lock */
 	struct mutex bitmap_lock; /* bitmap lock */
 	struct exfat_mount_options options;
@@ -331,6 +337,11 @@ static inline struct exfat_inode_info *EXFAT_I(struct inode *inode)
 	return container_of(inode, struct exfat_inode_info, vfs_inode);
 }
 
+static inline int exfat_forced_shutdown(struct super_block *sb)
+{
+	return test_bit(EXFAT_FLAGS_SHUTDOWN, &EXFAT_SB(sb)->s_exfat_flags);
+}
+
 /*
  * If ->i_mode can't hold 0222 (i.e. ATTR_RO), we use ->i_attrs to
  * save ATTR_RO instead of ->i_mode.
@@ -459,6 +470,7 @@ int exfat_file_fsync(struct file *file, loff_t start, loff_t end, int datasync);
 long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
 long exfat_compat_ioctl(struct file *filp, unsigned int cmd,
 				unsigned long arg);
+int exfat_force_shutdown(struct super_block *sb, u32 flags);
 
 /* namei.c */
 extern const struct dentry_operations exfat_dentry_ops;