[PATCH v3 20/33] ntfs: use the generic emergency read-only state

[Christian Brauner <brauner@kernel.org>]

Set SB_STATE_EMERGENCY_RO instead of the NV_EmergencyRO volume flag when
an error makes the volume read-only. ntfs_emergency_state() keeps
telling a shutdown (EIO) and the emergency state (EROFS) apart so all of
its callers stay as they are. /proc/mounts shows the volume read-only
again.

The VFS also refuses to freeze the superblock in that state. So
FS_IOC_SHUTDOWN with FS_SHUTDOWN_FLAGS_DEFAULT or _LOGFLUSH shuts down
without the freeze after an error, there's nothing left to flush
anyway.

Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/ntfs/super.c  | 14 +++++++++-----
 fs/ntfs/volume.h |  7 ++-----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index 91290688d2898..660fd145731fd 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -441,13 +441,12 @@ void ntfs_handle_error(struct super_block *sb)
 			sb->s_flags |= SB_RDONLY;
 		} else {
 			/*
-			 * NV_EmergencyRO makes the volume refuse modifications
-			 * instead and NV_Errors keeps it from being remounted
-			 * read-write. The error work marks the volume dirty on
-			 * disk.
+			 * SB_RDONLY needs s_umount, see sb_set_emergency_ro().
+			 * NV_Errors keeps the volume from being remounted
+			 * read-write and the error work marks it dirty.
 			 */
 			NVolSetErrors(vol);
-			if (test_and_set_bit(NV_EmergencyRO, &vol->flags))
+			if (!sb_set_emergency_ro(sb))
 				return;
 			queue_work(ntfs_wq, &vol->error_work);
 		}
@@ -2272,6 +2271,11 @@ int ntfs_force_shutdown(struct super_block *sb, u32 flags)
 	if (NVolShutdown(vol))
 		return 0;
 
+	/* After an error there is nothing to flush and freezing fails. */
+	if ((flags == FS_SHUTDOWN_FLAGS_DEFAULT ||
+	     flags == FS_SHUTDOWN_FLAGS_LOGFLUSH) && sb_emergency_ro(sb))
+		flags = FS_SHUTDOWN_FLAGS_NOLOGFLUSH;
+
 	switch (flags) {
 	case FS_SHUTDOWN_FLAGS_DEFAULT:
 	case FS_SHUTDOWN_FLAGS_LOGFLUSH:
diff --git a/fs/ntfs/volume.h b/fs/ntfs/volume.h
index 1ce81b260b15c..911a27983e138 100644
--- a/fs/ntfs/volume.h
+++ b/fs/ntfs/volume.h
@@ -16,6 +16,7 @@
 #include <linux/uidgid.h>
 #include <linux/workqueue.h>
 #include <linux/errseq.h>
+#include <linux/fs.h>
 
 #include "layout.h"
 
@@ -200,8 +201,6 @@ struct ntfs_volume {
  * NV_NativeSymlinkRel		Translate absolute Windows reparse targets (native_symlink=rel).
  * NV_MftBootstrap		Mount is still assembling $MFT's own runlist.
  * NV_StreamsWindows		Interpret the final path component as file:stream.
- * NV_EmergencyRO		An error made the volume read-only until it is
- *				unmounted (errors=remount-ro).
  */
 enum {
 	NV_Errors,
@@ -224,7 +223,6 @@ enum {
 	NV_SymlinkNative,
 	NV_MftBootstrap,
 	NV_StreamsWindows,
-	NV_EmergencyRO,
 };
 
 /*
@@ -266,14 +264,13 @@ DEFINE_NVOL_BIT_OPS(NativeSymlinkRel)
 DEFINE_NVOL_BIT_OPS(SymlinkNative)
 DEFINE_NVOL_BIT_OPS(MftBootstrap)
 DEFINE_NVOL_BIT_OPS(StreamsWindows)
-DEFINE_NVOL_BIT_OPS(EmergencyRO)
 
 /* -EIO after a shutdown, -EROFS after an error with errors=remount-ro */
 static inline int ntfs_emergency_state(struct ntfs_volume *vol)
 {
 	if (unlikely(NVolShutdown(vol)))
 		return -EIO;
-	if (unlikely(NVolEmergencyRO(vol)))
+	if (unlikely(sb_emergency_ro(vol->sb)))
 		return -EROFS;
 	return 0;
 }

-- 
2.53.0