On 1/15/25 19:07, Luis Henriques wrote: > Hi Bernd, > > On Wed, Jan 15 2025, Bernd Schubert wrote: > >> On 1/15/25 17:32, Luis Henriques wrote: >>> Currently userspace is able to notify the kernel to invalidate the cache >>> for an inode. This means that, if all the inodes in a filesystem need to >>> be invalidated, then userspace needs to iterate through all of them and do >>> this kernel notification separately. >>> >>> This patch adds a new option that allows userspace to invalidate all the >>> inodes with a single notification operation. In addition to invalidate all >>> the inodes, it also shrinks the superblock dcache. >> >> Out of interest, what is the use case? > > This is for a read-only filesystem. However, the filesystem objects > (files, directories, ...) may change dramatically in an atomic way, so > that a totally different set of objects replaces the old one. > > Obviously, this patch would help with the process of getting rid of the > old generation of the filesystem. > >>> >>> Signed-off-by: Luis Henriques <luis@xxxxxxxxxx> >>> --- >>> Just an additional note that this patch could eventually be simplified if >>> Dave Chinner patch to iterate through the superblock inodes[1] is merged. >>> >>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@xxxxxxxxxxxxx >>> >>> fs/fuse/inode.c | 53 +++++++++++++++++++++++++++++++++++++++ >>> include/uapi/linux/fuse.h | 3 +++ >>> 2 files changed, 56 insertions(+) >>> >>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c >>> index 3ce4f4e81d09..1fd9a5f303da 100644 >>> --- a/fs/fuse/inode.c >>> +++ b/fs/fuse/inode.c >>> @@ -546,6 +546,56 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid, >>> return NULL; >>> } >>> >>> +static int fuse_reverse_inval_all(struct fuse_conn *fc) >>> +{ >>> + struct fuse_mount *fm; >>> + struct super_block *sb; >>> + struct inode *inode, *old_inode = NULL; >>> + struct fuse_inode *fi; >>> + >>> + inode = fuse_ilookup(fc, FUSE_ROOT_ID, NULL); >>> + if (!inode) >>> + return -ENOENT; >>> + >>> + fm = get_fuse_mount(inode); >>> + iput(inode); >>> + if (!fm) >>> + return -ENOENT; >>> + sb = fm->sb; >>> + >>> + spin_lock(&sb->s_inode_list_lock); >>> + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { >> >> Maybe list_for_each_entry_safe() and then you can iput(inode) before the >> next iteration? > > I can rework this loop, but are you sure it's safe to use that? (Genuine > question!) > > I could only find two places where list_for_each_entry_safe() is being > used to walk through the sb inodes. And they both use an auxiliary list > that holds the inodes to be processed later. All other places use the > pattern I'm following here. > > Or did I misunderstood your suggestion? Actually my mistake, yeah you cannot use list_for_each_entry_safe() because you are giving up the list lock and the next entry, which is already obtained by _safe might not be valid anymore. Sorry for the noise! Thanks, Bernd
