Patch "netfs: Fix the (non-)cancellation of copy when cache is temporarily disabled" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    netfs: Fix the (non-)cancellation of copy when cache is temporarily disabled

to the 6.12-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:
     netfs-fix-the-non-cancellation-of-copy-when-cache-is.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1830a3cebd1a988697ffa193095aba899ceb58d0
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Fri Dec 13 13:50:10 2024 +0000

    netfs: Fix the (non-)cancellation of copy when cache is temporarily disabled
    
    [ Upstream commit d0327c824338cdccad058723a31d038ecd553409 ]
    
    When the caching for a cookie is temporarily disabled (e.g. due to a DIO
    write on that file), future copying to the cache for that file is disabled
    until all fds open on that file are closed.  However, if netfslib is using
    the deprecated PG_private_2 method (such as is currently used by ceph), and
    decides it wants to copy to the cache, netfs_advance_write() will just bail
    at the first check seeing that the cache stream is unavailable, and
    indicate that it dealt with all the content.
    
    This means that we have no subrequests to provide notifications to drive
    the state machine or even to pin the request and the request just gets
    discarded, leaving the folios with PG_private_2 set.
    
    Fix this by jumping directly to cancel the request if the cache is not
    available.  That way, we don't remove mark3 from the folio_queue list and
    netfs_pgpriv2_cancel() will clean up the folios.
    
    This was found by running the generic/013 xfstest against ceph with an
    active cache and the "-o fsc" option passed to ceph.  That would usually
    hang
    
    Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
    Reported-by: Max Kellermann <max.kellermann@xxxxxxxxx>
    Closes: https://lore.kernel.org/r/CAKPOu+_4m80thNy5_fvROoxBm689YtA0dZ-=gcmkzwYSY4syqw@xxxxxxxxxxxxxx/
    Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20241213135013.2964079-11-dhowells@xxxxxxxxxx
    cc: Jeff Layton <jlayton@xxxxxxxxxx>
    cc: Ilya Dryomov <idryomov@xxxxxxxxx>
    cc: Xiubo Li <xiubli@xxxxxxxxxx>
    cc: netfs@xxxxxxxxxxxxxxx
    cc: ceph-devel@xxxxxxxxxxxxxxx
    cc: linux-fsdevel@xxxxxxxxxxxxxxx
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c
index ba5af89d37fa..54d5004fec18 100644
--- a/fs/netfs/read_pgpriv2.c
+++ b/fs/netfs/read_pgpriv2.c
@@ -170,6 +170,10 @@ void netfs_pgpriv2_write_to_the_cache(struct netfs_io_request *rreq)
 
 	trace_netfs_write(wreq, netfs_write_trace_copy_to_cache);
 	netfs_stat(&netfs_n_wh_copy_to_cache);
+	if (!wreq->io_streams[1].avail) {
+		netfs_put_request(wreq, false, netfs_rreq_trace_put_return);
+		goto couldnt_start;
+	}
 
 	for (;;) {
 		error = netfs_pgpriv2_copy_folio(wreq, folio);