[PATCH 6.18 606/621] netfs, afs: Fix symlink reading

[Greg Kroah-Hartman]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells at redhat.com>

commit c51e89c5b5db3e1927738fad7cd18b66dde68aed upstream.

Fix the reading of symlinks from the cache in afs by making netfslib trim
the amount read down to i_size.  The problem is that afs sets the size of
the iterator to the size of the buffer (PAGE_SIZE) so that the cache can
round the read size up to the cache's DIO size.

Note that this also impacts the reading of AFS mountpoints as they're just
stored as symlinks with an odd file mode.

Link: https://patch.msgid.link/3912795.1789489319@warthog.procyon.org.uk
Fixes: c0410adf3da6 ("afs: Fix the locking used by afs_get_link()")
Reviewed-by: Paulo Alcantara <pc at manguebit.org>
cc: Paulo Alcantara <pc at manguebit.org>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
cc: netfs at lists.linux.dev
cc: linux-fsdevel at vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 fs/netfs/read_collect.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -409,6 +409,11 @@ static void netfs_rreq_assess_single(str
 		netfs_single_mark_inode_dirty(rreq->inode);
 	}
 
+	/* To do DIO, the cache has to round the size up, so we need to undo
+	 * the rounding.
+	 */
+	rreq->transferred = min(rreq->transferred, rreq->i_size);
+
 	if (rreq->iocb) {
 		rreq->iocb->ki_pos += rreq->transferred;
 		if (rreq->iocb->ki_complete) {