linux-kernel - Re: [PATCH 2/2][RFC][BUG] msync: updating ctime and mtime at syncing

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Date:	Sat, 12 Jan 2008 15:17:54 +0300
From:	"Anton Salikhmetov" <salikhmetov@...il.com>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Cc:	linux-mm@...ck.org, jakob@...hought.net,
	linux-kernel@...r.kernel.org, Valdis.Kletnieks@...edu,
	riel@...hat.com, ksm@...dk, staubach@...hat.com,
	jesper.juhl@...il.com
Subject: Re: [PATCH 2/2][RFC][BUG] msync: updating ctime and mtime at syncing

2008/1/12, Peter Zijlstra <a.p.zijlstra@...llo.nl>:
>
> On Fri, 2008-01-11 at 03:44 +0300, Anton Salikhmetov wrote:
>
> > +/*
> > + * Update the ctime and mtime stamps after checking if they are to be updated.
> > + */
> > +void mapped_file_update_time(struct file *file)
> > +{
> > +     if (test_and_clear_bit(AS_MCTIME, &file->f_mapping->flags)) {
> > +             get_file(file);
> > +             file_update_time(file);
> > +             fput(file);
> > +     }
> > +}
> > +
>
> I don't think you need the get/put file stuff here, because
>
> > @@ -87,6 +87,8 @@ long do_fsync(struct file *file, int datasync)
> >               goto out;
> >       }
> >
> > +     mapped_file_update_time(file);
> > +
> >       ret = filemap_fdatawrite(mapping);
> >
> >       /*
>
> at this call-site we already hold an extra reference on the file, and
>
> > @@ -74,14 +79,17 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
> >                       break;
> >               }
> >               file = vma->vm_file;
> > -             if ((flags & MS_SYNC) && file && (vma->vm_flags & VM_SHARED)) {
> > -                     get_file(file);
> > -                     up_read(&mm->mmap_sem);
> > -                     error = do_fsync(file, 0);
> > -                     fput(file);
> > -                     if (error)
> > -                             return error;
> > -                     down_read(&mm->mmap_sem);
> > +             if (file && (vma->vm_flags & VM_SHARED)) {
> > +                     mapped_file_update_time(file);
> > +                     if (flags & MS_SYNC) {
> > +                             get_file(file);
> > +                             up_read(&mm->mmap_sem);
> > +                             error = do_fsync(file, 0);
> > +                             fput(file);
> > +                             if (error)
> > +                                     return error;
> > +                             down_read(&mm->mmap_sem);
> > +                     }
> >               }
> >
> >               start = vma->vm_end;
>
> here we hold the mmap_sem so the vma reference on the file can't go
> away.

These get_file() and fput() calls were in the sys_msync() function form before
all my changes. I did not add them here.

>
>
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