The if(mm) check is not required in find_vma, as the kernel code calls find_vma only when it is absolutely sure that the mm_struct arg to it is non-NULL. Removing the if(mm) check and adding the a WARN_ONCE(!mm) for now. This will serve the purpose of mandating that the execution context(user-mode/kernel-mode) be known before find_vma is called. Also fixed 2 checkpatch.pl errors in the declaration of the rb_node and vma_tmp local variables. I was browsing through the internet and read a discussion at https://lkml.org/lkml/2012/3/27/342 which discusses removal of the validation check within find_vma. Since no-one responded, I decided to send this patch with Andrew's suggestions. Signed-off-by: Rajman Mekaco <rajman.mekaco@xxxxxxxxx> Cc: Kautuk Consul <consul.kautuk@xxxxxxxxx> --- mm/mmap.c | 53 +++++++++++++++++++++++++++-------------------------- 1 files changed, 27 insertions(+), 26 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index b38b47e..1c3ef5d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1616,33 +1616,34 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) { struct vm_area_struct *vma = NULL; - if (mm) { - /* Check the cache first. */ - /* (Cache hit rate is typically around 35%.) */ - vma = mm->mmap_cache; - if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) { - struct rb_node * rb_node; - - rb_node = mm->mm_rb.rb_node; - vma = NULL; - - while (rb_node) { - struct vm_area_struct * vma_tmp; - - vma_tmp = rb_entry(rb_node, - struct vm_area_struct, vm_rb); - - if (vma_tmp->vm_end > addr) { - vma = vma_tmp; - if (vma_tmp->vm_start <= addr) - break; - rb_node = rb_node->rb_left; - } else - rb_node = rb_node->rb_right; - } - if (vma) - mm->mmap_cache = vma; + if (WARN_ON_ONCE(!mm)) + return NULL; + + /* Check the cache first. */ + /* (Cache hit rate is typically around 35%.) */ + vma = mm->mmap_cache; + if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) { + struct rb_node *rb_node; + + rb_node = mm->mm_rb.rb_node; + vma = NULL; + + while (rb_node) { + struct vm_area_struct *vma_tmp; + + vma_tmp = rb_entry(rb_node, + struct vm_area_struct, vm_rb); + + if (vma_tmp->vm_end > addr) { + vma = vma_tmp; + if (vma_tmp->vm_start <= addr) + break; + rb_node = rb_node->rb_left; + } else + rb_node = rb_node->rb_right; } + if (vma) + mm->mmap_cache = vma; } return vma; } -- 1.7.5.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>