From 1bd9c4e4f0494915b2391f373d25096579f835ff Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 18 Nov 2021 08:58:08 +0000 Subject: vfs, cachefiles: Mark a backing file in use with an inode flag Use an inode flag, S_KERNEL_FILE, to mark that a backing file is in use by the kernel to prevent cachefiles or other kernel services from interfering with that file. Alter rmdir to reject attempts to remove a directory marked with this flag. This is used by cachefiles to prevent cachefilesd from removing them. Using S_SWAPFILE instead isn't really viable as that has other effects in the I/O paths. Changes ======= ver #3: - Check for the object pointer being NULL in the tracepoints rather than the caller. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819630256.215744.4815885535039369574.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906931596.143852.8642051223094013028.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967141000.1823006.12920680657559677789.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021541207.640689.564689725898537127.stgit@warthog.procyon.org.uk/ # v4 --- fs/namei.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 1f9d2187c765..d81f04f8d818 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3958,7 +3958,8 @@ int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir, inode_lock(dentry->d_inode); error = -EBUSY; - if (is_local_mountpoint(dentry)) + if (is_local_mountpoint(dentry) || + (dentry->d_inode->i_flags & S_KERNEL_FILE)) goto out; error = security_inode_rmdir(dir, dentry); -- cgit v1.2.3