This is a note to let you know that I've just added the patch titled
fuse: make sure reclaim doesn't write the inode
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fuse-make-sure-reclaim-doesn-t-write-the-inode.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5c791fe1e2a4f401f819065ea4fc0450849f1818 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Date: Fri, 22 Oct 2021 17:03:01 +0200
Subject: fuse: make sure reclaim doesn't write the inode
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
commit 5c791fe1e2a4f401f819065ea4fc0450849f1818 upstream.
In writeback cache mode mtime/ctime updates are cached, and flushed to the
server using the ->write_inode() callback.
Closing the file will result in a dirty inode being immediately written,
but in other cases the inode can remain dirty after all references are
dropped. This result in the inode being written back from reclaim, which
can deadlock on a regular allocation while the request is being served.
The usual mechanisms (GFP_NOFS/PF_MEMALLOC*) don't work for FUSE, because
serving a request involves unrelated userspace process(es).
Instead do the same as for dirty pages: make sure the inode is written
before the last reference is gone.
- fallocate(2)/copy_file_range(2): these call file_update_time() or
file_modified(), so flush the inode before returning from the call
- unlink(2), link(2) and rename(2): these call fuse_update_ctime(), so
flush the ctime directly from this helper
Reported-by: chenguanyou <chenguanyou@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Ed Tsai <ed.tsai@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/fuse/dir.c | 8 ++++++++
fs/fuse/file.c | 15 +++++++++++++++
fs/fuse/fuse_i.h | 1 +
fs/fuse/inode.c | 3 +++
4 files changed, 27 insertions(+)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -791,11 +791,19 @@ static int fuse_symlink(struct inode *di
return create_new_entry(fm, &args, dir, entry, S_IFLNK);
}
+void fuse_flush_time_update(struct inode *inode)
+{
+ int err = sync_inode_metadata(inode, 1);
+
+ mapping_set_error(inode->i_mapping, err);
+}
+
void fuse_update_ctime(struct inode *inode)
{
if (!IS_NOCMTIME(inode)) {
inode->i_ctime = current_time(inode);
mark_inode_dirty_sync(inode);
+ fuse_flush_time_update(inode);
}
}
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1849,6 +1849,17 @@ int fuse_write_inode(struct inode *inode
struct fuse_file *ff;
int err;
+ /*
+ * Inode is always written before the last reference is dropped and
+ * hence this should not be reached from reclaim.
+ *
+ * Writing back the inode from reclaim can deadlock if the request
+ * processing itself needs an allocation. Allocations triggering
+ * reclaim while serving a request can't be prevented, because it can
+ * involve any number of unrelated userspace processes.
+ */
+ WARN_ON(wbc->for_reclaim);
+
ff = __fuse_write_file_get(fc, fi);
err = fuse_flush_times(inode, ff);
if (ff)
@@ -3338,6 +3349,8 @@ out:
if (lock_inode)
inode_unlock(inode);
+ fuse_flush_time_update(inode);
+
return err;
}
@@ -3447,6 +3460,8 @@ out:
inode_unlock(inode_out);
file_accessed(file_in);
+ fuse_flush_time_update(inode_out);
+
return err;
}
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1113,6 +1113,7 @@ int fuse_allow_current_process(struct fu
u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);
+void fuse_flush_time_update(struct inode *inode);
void fuse_update_ctime(struct inode *inode);
int fuse_update_attributes(struct inode *inode, struct file *file);
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -119,6 +119,9 @@ static void fuse_evict_inode(struct inod
{
struct fuse_inode *fi = get_fuse_inode(inode);
+ /* Will write inode on close/munmap and in all other dirtiers */
+ WARN_ON(inode->i_state & I_DIRTY_INODE);
+
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
if (inode->i_sb->s_flags & SB_ACTIVE) {
Patches currently in stable-queue which might be from mszeredi@xxxxxxxxxx are
queue-5.10/fuse-make-sure-reclaim-doesn-t-write-the-inode.patch
