From: Michel Lespinasse <walken@xxxxxxxxxx> Subject: mmap locking API: convert nested write lock sites Add API for nested write locks and convert the few call sites doing that. Link: http://lkml.kernel.org/r/20200520052908.204642-7-walken@xxxxxxxxxx Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Reviewed-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Davidlohr Bueso <dbueso@xxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Liam Howlett <Liam.Howlett@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Ying Han <yinghan@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/um/include/asm/mmu_context.h | 3 ++- include/linux/mmap_lock.h | 5 +++++ kernel/fork.c | 2 +- 3 files changed, 8 insertions(+), 2 deletions(-) --- a/arch/um/include/asm/mmu_context.h~mmap-locking-api-convert-nested-write-lock-sites +++ a/arch/um/include/asm/mmu_context.h @@ -8,6 +8,7 @@ #include <linux/sched.h> #include <linux/mm_types.h> +#include <linux/mmap_lock.h> #include <asm/mmu.h> @@ -47,7 +48,7 @@ static inline void activate_mm(struct mm * when the new ->mm is used for the first time. */ __switch_mm(&new->context.id); - down_write_nested(&new->mmap_sem, 1); + mmap_write_lock_nested(new, SINGLE_DEPTH_NESTING); uml_setup_stubs(new); mmap_write_unlock(new); } --- a/include/linux/mmap_lock.h~mmap-locking-api-convert-nested-write-lock-sites +++ a/include/linux/mmap_lock.h @@ -11,6 +11,11 @@ static inline void mmap_write_lock(struc down_write(&mm->mmap_sem); } +static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass) +{ + down_write_nested(&mm->mmap_sem, subclass); +} + static inline int mmap_write_lock_killable(struct mm_struct *mm) { return down_write_killable(&mm->mmap_sem); --- a/kernel/fork.c~mmap-locking-api-convert-nested-write-lock-sites +++ a/kernel/fork.c @@ -501,7 +501,7 @@ static __latent_entropy int dup_mmap(str /* * Not linked in yet - no deadlock potential: */ - down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); + mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); /* No ordering required: file already has been exposed. */ RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); _
