Revert "mm: introduce PF_MEMALLOC_NORECLAIM, PF_MEMALLOC_NOWARN"

This reverts commit eab0af905bfc3e9c05da2ca163d76a1513159aa4.

There is no existing user of those flags.  PF_MEMALLOC_NOWARN is dangerous
because a nested allocation context can use GFP_NOFAIL which could cause
unexpected failure.  Such a code would be hard to maintain because it
could be deeper in the call chain.

PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1] that
such a allocation contex is inherently unsafe if the context doesn't fully
control all allocations called from this context.

While PF_MEMALLOC_NOWARN is not dangerous the way PF_MEMALLOC_NORECLAIM is
it doesn't have any user and as Matthew has pointed out we are running out
of those flags so better reclaim it without any real users.

[1] https://lore.kernel.org/all/ZcM0xtlKbAOFjv5n@tiehlicka/

Link: https://lkml.kernel.org/r/20240926172940.167084-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: James Morris <jmorris@namei.org>
Cc: Jan Kara <jack@suse.cz>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e6ee4258169a0e17838b4d05ce38cac28056a95f..449dd64ed9acc769d3de0cc10758aa0a562cff89 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1681,8 +1681,8 @@ extern struct pid *cad_pid;
                                                 * I am cleaning dirty pages from some other bdi. */
 #define PF_KTHREAD             0x00200000      /* I am a kernel thread */
 #define PF_RANDOMIZE           0x00400000      /* Randomize virtual address space */
-#define PF_MEMALLOC_NORECLAIM  0x00800000      /* All allocation requests will clear __GFP_DIRECT_RECLAIM */
-#define PF_MEMALLOC_NOWARN     0x01000000      /* All allocation requests will inherit __GFP_NOWARN */
+#define PF__HOLE__00800000     0x00800000
+#define PF__HOLE__01000000     0x01000000
 #define PF__HOLE__02000000     0x02000000
 #define PF_NO_SETAFFINITY      0x04000000      /* Userland is not allowed to meddle with cpus_mask */
 #define PF_MCE_EARLY           0x08000000      /* Early kill for mce process policy */

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 07bb8d4181d7ee6a03aeb3c7dea2a17773861c45..928a626725e69ab4ce4b3b14a2ffa832499d5055 100644 (file)
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -251,25 +251,16 @@ static inline gfp_t current_gfp_context(gfp_t flags)
 {
        unsigned int pflags = READ_ONCE(current->flags);
 
-       if (unlikely(pflags & (PF_MEMALLOC_NOIO |
-                              PF_MEMALLOC_NOFS |
-                              PF_MEMALLOC_NORECLAIM |
-                              PF_MEMALLOC_NOWARN |
-                              PF_MEMALLOC_PIN))) {
+       if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) {
                /*
-                * Stronger flags before weaker flags:
-                * NORECLAIM implies NOIO, which in turn implies NOFS
+                * NOIO implies both NOIO and NOFS and it is a weaker context
+                * so always make sure it makes precedence
                 */
-               if (pflags & PF_MEMALLOC_NORECLAIM)
-                       flags &= ~__GFP_DIRECT_RECLAIM;
-               else if (pflags & PF_MEMALLOC_NOIO)
+               if (pflags & PF_MEMALLOC_NOIO)
                        flags &= ~(__GFP_IO | __GFP_FS);
                else if (pflags & PF_MEMALLOC_NOFS)
                        flags &= ~__GFP_FS;
 
-               if (pflags & PF_MEMALLOC_NOWARN)
-                       flags |= __GFP_NOWARN;
-
                if (pflags & PF_MEMALLOC_PIN)
                        flags &= ~__GFP_MOVABLE;
        }