From: Michal Hocko <mhocko@xxxxxxxx> commit 9a8da05d7ad619beb84d0c6904c3fa7022c6fb9b upstream. 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@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx> Cc: Paul Moore <paul@xxxxxxxxxxxxxx> Cc: Serge E. Hallyn <serge@xxxxxxxxxx> Cc: Yafang Shao <laoar.shao@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/sched.h | 4 ++-- include/linux/sched/mm.h | 17 ++++------------- 2 files changed, 6 insertions(+), 15 deletions(-) --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1659,8 +1659,8 @@ 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 */ --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -258,25 +258,16 @@ static inline gfp_t current_gfp_context( { 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; } Patches currently in stable-queue which might be from mhocko@xxxxxxxx are queue-6.11/revert-mm-introduce-pf_memalloc_noreclaim-pf_memalloc_nowarn.patch
