bcachefs: do not use PF_MEMALLOC_NORECLAIM

Patch series "remove PF_MEMALLOC_NORECLAIM" v3.


This patch (of 2):

bch2_new_inode relies on PF_MEMALLOC_NORECLAIM to try to allocate a new
inode to achieve GFP_NOWAIT semantic while holding locks. If this
allocation fails it will drop locks and use GFP_NOFS allocation context.

We would like to drop PF_MEMALLOC_NORECLAIM because it is really
dangerous to use if the caller doesn't control the full call chain with
this flag set. E.g. if any of the function down the chain needed
GFP_NOFAIL request the PF_MEMALLOC_NORECLAIM would override this and
cause unexpected failure.

While this is not the case in this particular case using the scoped gfp
semantic is not really needed bacause we can easily pus the allocation
context down the chain without too much clutter.

[akpm@linux-foundation.org: fix kerneldoc warnings]
Link: https://lkml.kernel.org/r/20240926172940.167084-1-mhocko@kernel.org
Link: https://lkml.kernel.org/r/20240926172940.167084-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz> # For vfs changes
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: James Morris <jmorris@namei.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/security/security.c b/security/security.c
index 6875eb4a59fc..c5981e558bc2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -740,19 +740,20 @@ static int lsm_file_alloc(struct file *file)
 /**
  * lsm_inode_alloc - allocate a composite inode blob
  * @inode: the inode that needs a blob
+ * @gfp: allocation flags
  *
  * Allocate the inode blob for all the modules
  *
  * Returns 0, or -ENOMEM if memory can't be allocated.
  */
-static int lsm_inode_alloc(struct inode *inode)
+static int lsm_inode_alloc(struct inode *inode, gfp_t gfp)
 {
 	if (!lsm_inode_cache) {
 		inode->i_security = NULL;
 		return 0;
 	}
 
-	inode->i_security = kmem_cache_zalloc(lsm_inode_cache, GFP_NOFS);
+	inode->i_security = kmem_cache_zalloc(lsm_inode_cache, gfp);
 	if (inode->i_security == NULL)
 		return -ENOMEM;
 	return 0;
@@ -1678,6 +1679,7 @@ int security_path_notify(const struct path *path, u64 mask,
 /**
  * security_inode_alloc() - Allocate an inode LSM blob
  * @inode: the inode
+ * @gfp: allocation flags
  *
  * Allocate and attach a security structure to @inode->i_security.  The
  * i_security field is initialized to NULL when the inode structure is
@@ -1685,9 +1687,9 @@ int security_path_notify(const struct path *path, u64 mask,
  *
  * Return: Return 0 if operation was successful.
  */
-int security_inode_alloc(struct inode *inode)
+int security_inode_alloc(struct inode *inode, gfp_t gfp)
 {
-	int rc = lsm_inode_alloc(inode);
+	int rc = lsm_inode_alloc(inode, gfp);
 
 	if (unlikely(rc))
 		return rc;