When a mount is marked read-only we set MNT_WRITE_HOLD on it if there
aren't currently any active writers. Split this logic out into simple
helpers that we can use in follow-up patches.
Suggested-by: Christoph Hellwig <hch@xxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
/* v2 */
patch not present
/* v3 */
patch not present
/* v4 */
patch introduced
/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837
---
fs/namespace.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 5177bf6d810e..4aab396e5f21 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -469,10 +469,8 @@ void mnt_drop_write_file(struct file *file)
}
EXPORT_SYMBOL(mnt_drop_write_file);
-static int mnt_make_readonly(struct mount *mnt)
+static inline int mnt_hold_writers(struct mount *mnt)
{
- int ret = 0;
-
mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
/*
* After storing MNT_WRITE_HOLD, we'll read the counters. This store
@@ -497,15 +495,29 @@ static int mnt_make_readonly(struct mount *mnt)
* we're counting up here.
*/
if (mnt_get_writers(mnt) > 0)
- ret = -EBUSY;
- else
- mnt->mnt.mnt_flags |= MNT_READONLY;
+ return -EBUSY;
+
+ return 0;
+}
+
+static inline void mnt_unhold_writers(struct mount *mnt)
+{
/*
* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
* that become unheld will see MNT_READONLY.
*/
smp_wmb();
mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
+}
+
+static int mnt_make_readonly(struct mount *mnt)
+{
+ int ret;
+
+ ret = mnt_hold_writers(mnt);
+ if (!ret)
+ mnt->mnt.mnt_flags |= MNT_READONLY;
+ mnt_unhold_writers(mnt);
return ret;
}
--
2.30.0
