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Date: Tue, 22 May 2012 08:11:49 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: john stultz <johnstul@...ibm.com>
cc: Arve Hjonnevag <arve@...roid.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Hellwig <hch@...radead.org>,
Cong Wang <amwang@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>,
Colin Cross <ccross@...roid.com>,
John Stultz <john.stultz@...aro.org>,
Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger@...ger.ca>,
Mark Fasheh <mfasheh@...e.de>,
Joel Becker <jlbec@...lplan.org>,
Dave Chinner <david@...morbit.com>, Ben Myers <bpm@....com>,
Michael Kerrisk <mtk.manpages@...il.com>, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/10] mm/fs: route MADV_REMOVE to FALLOC_FL_PUNCH_HOLE
On Mon, 21 May 2012, john stultz wrote:
> On Sat, May 12, 2012 at 5:13 AM, Hugh Dickins <hughd@...gle.com> wrote:
> > Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
> > to use do_fallocate() instead of vmtruncate_range(): which extends
> > madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.
> >
> > There is one more user of vmtruncate_range() in our tree, staging/android's
> > ashmem_shrink(): convert it to use do_fallocate() too (but if its unpinned
> > areas are already unmapped - I don't know - then it would do better to use
> > shmem_truncate_range() directly).
>
> I suspect shmem_truncate_range directly would be the right approach,
> but am not totally sure.
> Arve: Any thoughts?
>
> Hugh: Do you have a git tree with this set available somewhere? I was
> working on my own tmpfs support for FALLOC_FL_PUNCH_HOLE, along with
> my volatile range work, so I'd like to rebase on top of your work
> here.
I don't, no, just the patch series posted.
I had hoped by now to say that it's in linux-next (though it would be
at the daily rebased end, which probably doesn't help you), but not yet.
If shmem_truncate_range() is all you need, then that doesn't depend on
these patches at all - but I expect you are aiming to be more general.
Hugh
>
> thanks
> -john
>
>
> >
> > Based-on-patch-by: Cong Wang <amwang@...hat.com>
> > Signed-off-by: Hugh Dickins <hughd@...gle.com>
> > ---
> > drivers/staging/android/ashmem.c | 8 +++++---
> > mm/madvise.c | 15 +++++++--------
> > 2 files changed, 12 insertions(+), 11 deletions(-)
> >
> > --- 3045N.orig/drivers/staging/android/ashmem.c 2012-05-05 10:42:33.564056626 -0700
> > +++ 3045N/drivers/staging/android/ashmem.c 2012-05-05 10:46:25.692062478 -0700
> > @@ -19,6 +19,7 @@
> > #include <linux/module.h>
> > #include <linux/file.h>
> > #include <linux/fs.h>
> > +#include <linux/falloc.h>
> > #include <linux/miscdevice.h>
> > #include <linux/security.h>
> > #include <linux/mm.h>
> > @@ -363,11 +364,12 @@ static int ashmem_shrink(struct shrinker
> >
> > mutex_lock(&ashmem_mutex);
> > list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
> > - struct inode *inode = range->asma->file->f_dentry->d_inode;
> > loff_t start = range->pgstart * PAGE_SIZE;
> > - loff_t end = (range->pgend + 1) * PAGE_SIZE - 1;
> > + loff_t end = (range->pgend + 1) * PAGE_SIZE;
> >
> > - vmtruncate_range(inode, start, end);
> > + do_fallocate(range->asma->file,
> > + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> > + start, end - start);
> > range->purged = ASHMEM_WAS_PURGED;
> > lru_del(range);
> >
> > --- 3045N.orig/mm/madvise.c 2012-05-05 10:42:33.572056784 -0700
> > +++ 3045N/mm/madvise.c 2012-05-05 10:46:25.692062478 -0700
> > @@ -11,8 +11,10 @@
> > #include <linux/mempolicy.h>
> > #include <linux/page-isolation.h>
> > #include <linux/hugetlb.h>
> > +#include <linux/falloc.h>
> > #include <linux/sched.h>
> > #include <linux/ksm.h>
> > +#include <linux/fs.h>
> >
> > /*
> > * Any behaviour which results in changes to the vma->vm_flags needs to
> > @@ -200,8 +202,7 @@ static long madvise_remove(struct vm_are
> > struct vm_area_struct **prev,
> > unsigned long start, unsigned long end)
> > {
> > - struct address_space *mapping;
> > - loff_t offset, endoff;
> > + loff_t offset;
> > int error;
> >
> > *prev = NULL; /* tell sys_madvise we drop mmap_sem */
> > @@ -217,16 +218,14 @@ static long madvise_remove(struct vm_are
> > if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
> > return -EACCES;
> >
> > - mapping = vma->vm_file->f_mapping;
> > -
> > offset = (loff_t)(start - vma->vm_start)
> > + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> > - endoff = (loff_t)(end - vma->vm_start - 1)
> > - + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> >
> > - /* vmtruncate_range needs to take i_mutex */
> > + /* filesystem's fallocate may need to take i_mutex */
> > up_read(¤t->mm->mmap_sem);
> > - error = vmtruncate_range(mapping->host, offset, endoff);
> > + error = do_fallocate(vma->vm_file,
> > + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> > + offset, end - start);
> > down_read(¤t->mm->mmap_sem);
> > return error;
> > }
> > --
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