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afs: Remove setting of AS_RELEASE_ALWAYS for symlinks and mountpoints

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Regular AFS files correctly use afs_file_aops which have release_folio
set as netfs_release_folio, so AS_RELEASE_ALWAYS is valid for them
when fscache is enabled (set via afs_vnode_set_cache()).
Symlinks and mountpoints in AFS use afs_dir_aops, which does not provide
a release_folio callback. However, afs_apply_status() unconditionally
calls mapping_set_release_always() for these.

In such case when memory management code attempts to release folios,
filemap_release_folio() checks folio_needs_release() which
returns true due to AS_RELEASE_ALWAYS being set. Since there is no
release_folio callback, it falls through to try_to_free_buffers(),
which at present expects buffer_heads to be not null. For symlinks
and mountpoints without buffer_heads, this causes pointer dereference.

[dh: Added more bits that were missed]

Fixes: eae9e78951 ("afs: Use netfslib for symlinks, allowing them to be cached")
Signed-off-by: Deepakkumar Karn <dkarn@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260622090856.2746629-6-dhowells@redhat.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
David Howells 2026-06-22 10:08:39 +01:00 committed by Christian Brauner
parent 733a984a4e
commit 81e985b4c3
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2 changed files with 3 additions and 6 deletions
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7
fs/afs/inode.c
View File

@ -52,9 +52,9 @@ static noinline void dump_vnode(struct afs_vnode *vnode, struct afs_vnode *paren
/*
* Set parameters for the netfs library
*/
static void afs_set_netfs_context(struct afs_vnode *vnode)
static void afs_set_netfs_context(struct afs_vnode *vnode, bool is_file)
{
netfs_inode_init(&vnode->netfs, &afs_req_ops, true);
netfs_inode_init(&vnode->netfs, &afs_req_ops, is_file);
}
/*
@ -126,7 +126,6 @@ static int afs_inode_init_from_status(struct afs_operation *op,
}
inode->i_mapping->a_ops = &afs_symlink_aops;
inode_nohighmem(inode);
mapping_set_release_always(inode->i_mapping);
break;
default:
dump_vnode(vnode, op->file[0].vnode != vnode ? op->file[0].vnode : NULL);
@ -136,7 +135,7 @@ static int afs_inode_init_from_status(struct afs_operation *op,
i_size_write(inode, status->size);
inode_set_bytes(inode, status->size);
afs_set_netfs_context(vnode);
afs_set_netfs_context(vnode, status->type == AFS_FTYPE_FILE);
vnode->invalid_before = status->data_version;
trace_afs_set_dv(vnode, status->data_version);

2
fs/afs/internal.h
View File

@ -750,8 +750,6 @@ static inline void afs_vnode_set_cache(struct afs_vnode *vnode,
{
#ifdef CONFIG_AFS_FSCACHE
vnode->netfs.cache = cookie;
if (cookie)
mapping_set_release_always(vnode->netfs.inode.i_mapping);
#endif
}