Messages in this thread | | | Subject | Re: [PATCH -v5 1/2] Massive code cleanup of sys_msync() | From | Miklos Szeredi <> | Date | Thu, 17 Jan 2008 12:01:18 +0100 |
| |
> Substantial code cleanup of the sys_msync() function: > > 1) using the PAGE_ALIGN() macro instead of "manual" alignment; > 2) improved readability of the loop traversing the process memory regions. > > Signed-off-by: Anton Salikhmetov <salikhmetov@gmail.com> > --- > mm/msync.c | 74 +++++++++++++++++++++++++++++------------------------------ > 1 files changed, 36 insertions(+), 38 deletions(-) > > diff --git a/mm/msync.c b/mm/msync.c > index 144a757..44997bf 100644 > --- a/mm/msync.c > +++ b/mm/msync.c > @@ -1,24 +1,22 @@ > /* > - * linux/mm/msync.c > + * The msync() system call. > * > - * Copyright (C) 1994-1999 Linus Torvalds > + * Copyright (C) 1994-1999 Linus Torvalds > + * Copyright (C) 2008 Anton Salikhmetov <salikhmetov@gmail.com> > */ > > -/* > - * The msync() system call. > - */ > +#include <linux/file.h> > #include <linux/fs.h> > #include <linux/mm.h> > #include <linux/mman.h> > -#include <linux/file.h> > -#include <linux/syscalls.h> > #include <linux/sched.h> > +#include <linux/syscalls.h> > > /* > * MS_SYNC syncs the entire file - including mappings. > * > * MS_ASYNC does not start I/O (it used to, up to 2.5.67). > - * Nor does it marks the relevant pages dirty (it used to up to 2.6.17). > + * Nor does it mark the relevant pages dirty (it used to up to 2.6.17). > * Now it doesn't do anything, since dirty pages are properly tracked. > * > * The application may now run fsync() to > @@ -33,8 +31,7 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags) > unsigned long end; > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > - int unmapped_error = 0; > - int error = -EINVAL; > + int error = -EINVAL, unmapped_error = 0;
I prefer multi-line variable declarations, especially for ones with an initializer.
> > if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) > goto out; > @@ -42,62 +39,63 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags) > goto out; > if ((flags & MS_ASYNC) && (flags & MS_SYNC)) > goto out; > - error = -ENOMEM; > - len = (len + ~PAGE_MASK) & PAGE_MASK; > + > + len = PAGE_ALIGN(len); > end = start + len; > - if (end < start) > + if (end < start) { > + error = -ENOMEM;
The usual style is to have the error assignment outside the conditional. That way is shorter, clearer, as well as possibly generating better code.
> goto out; > + } > + > error = 0; > +
Unnecessary empty line here, these two statements actually belong together.
> if (end == start) > goto out; > + > /* > * If the interval [start,end) covers some unmapped address ranges, > * just ignore them, but return -ENOMEM at the end. > */ > down_read(&mm->mmap_sem); > vma = find_vma(mm, start); > - for (;;) { > + do { > struct file *file; > > - /* Still start < end. */ > - error = -ENOMEM; > - if (!vma) > - goto out_unlock; > - /* Here start < vma->vm_end. */ > + if (!vma) { > + error = -ENOMEM; > + break; > + }
Again, error asignment should be outside the conditional. This of course means, you'll have to set the error back to zero at the end of the loop, but that's fine.
> if (start < vma->vm_start) { > start = vma->vm_start; > - if (start >= end) > - goto out_unlock; > + if (start >= end) { > + error = -ENOMEM; > + break; > + }
Ditto.
> unmapped_error = -ENOMEM; > } > - /* Here vma->vm_start <= start < vma->vm_end. */ > - if ((flags & MS_INVALIDATE) && > - (vma->vm_flags & VM_LOCKED)) { > + if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED)) { > error = -EBUSY;
Ditto2.
> - goto out_unlock; > + break; > } > - file = vma->vm_file; > start = vma->vm_end; > - if ((flags & MS_SYNC) && file && > - (vma->vm_flags & VM_SHARED)) { > + > + file = vma->vm_file; > + if (file && (vma->vm_flags & VM_SHARED) && (flags & MS_SYNC)) { > get_file(file); > up_read(&mm->mmap_sem); > error = do_fsync(file, 0); > fput(file); > - if (error || start >= end) > + if (error)
This simplifies, but also does unnecessary down/find_vma/up.
> goto out; > down_read(&mm->mmap_sem); > vma = find_vma(mm, start); > - } else { > - if (start >= end) { > - error = 0; > - goto out_unlock; > - } > - vma = vma->vm_next; > + continue; > } > - } > -out_unlock: > + > + vma = vma->vm_next; > + } while (start < end); > up_read(&mm->mmap_sem); > + > out: > - return error ? : unmapped_error; > + return error ? error : unmapped_error; > }
| |