[PATCH v6 32/40] fs: split out functions to hold writers
From: Christian Brauner <hidden>
Date: 2021-01-21 13:34:42
Also in:
linux-ext4, linux-fsdevel, linux-integrity, linux-security-module, linux-xfs, selinux
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
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. Link: https://lore.kernel.org/r/20210112220124.837960-5-christian.brauner@ubuntu.com (local) Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <redacted> --- /* v2 */ patch not present /* v3 */ patch not present /* v4 */ patch introduced /* v5 */ unchanged base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837 /* v6 */ unchanged base-commit: 19c329f6808995b142b3966301f217c831e7cf31 --- fs/namespace.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 367f1c7cb6db..774ae5f74716 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c@@ -470,10 +470,8 @@ 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
@@ -498,15 +496,29 @@ 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