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Message-ID: <65qj4iqgdzebrg5cqwaocjzswenzzgoifdnewrhoipieqi3d5v@bxxupemsgsbs>
Date: Tue, 21 May 2024 11:38:33 +0000
From: Daniel Gomez <da.gomez@...sung.com>
To: "Darrick J. Wong" <djwong@...nel.org>
CC: "hughd@...gle.com" <hughd@...gle.com>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "willy@...radead.org" <willy@...radead.org>,
	"jack@...e.cz" <jack@...e.cz>, "mcgrof@...nel.org" <mcgrof@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-xfs@...r.kernel.org"
	<linux-xfs@...r.kernel.org>, Pankaj Raghav <p.raghav@...sung.com>,
	"dagmcr@...il.com" <dagmcr@...il.com>, "yosryahmed@...gle.com"
	<yosryahmed@...gle.com>, "baolin.wang@...ux.alibaba.com"
	<baolin.wang@...ux.alibaba.com>, "ritesh.list@...il.com"
	<ritesh.list@...il.com>, "lsf-pc@...ts.linux-foundation.org"
	<lsf-pc@...ts.linux-foundation.org>, "david@...hat.com" <david@...hat.com>,
	"chandan.babu@...cle.com" <chandan.babu@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"brauner@...nel.org" <brauner@...nel.org>
Subject: Re: [PATCH 11/12] shmem: add file length arg in shmem_get_folio()
 path

On Fri, May 17, 2024 at 09:17:41AM -0700, Darrick J. Wong wrote:
> On Wed, May 15, 2024 at 05:57:36AM +0000, Daniel Gomez wrote:
> > In preparation for large folio in the write and fallocate paths, add
> > file length argument in shmem_get_folio() path to be able to calculate
> > the folio order based on the file size. Use of order-0 (PAGE_SIZE) for
> > read, page cache read, and vm fault.
> > 
> > This enables high order folios in the write and fallocate path once the
> > folio order is calculated based on the length.
> > 
> > Signed-off-by: Daniel Gomez <da.gomez@...sung.com>
> > ---
> >  fs/xfs/scrub/xfile.c     |  6 +++---
> >  fs/xfs/xfs_buf_mem.c     |  3 ++-
> >  include/linux/shmem_fs.h |  2 +-
> >  mm/khugepaged.c          |  3 ++-
> >  mm/shmem.c               | 35 ++++++++++++++++++++---------------
> >  mm/userfaultfd.c         |  2 +-
> >  6 files changed, 29 insertions(+), 22 deletions(-)
> > 
> > diff --git a/fs/xfs/scrub/xfile.c b/fs/xfs/scrub/xfile.c
> > index 8cdd863db585..4905f5e4cb5d 100644
> > --- a/fs/xfs/scrub/xfile.c
> > +++ b/fs/xfs/scrub/xfile.c
> > @@ -127,7 +127,7 @@ xfile_load(
> >  		unsigned int	offset;
> >  
> >  		if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
> > -				SGP_READ) < 0)
> > +				SGP_READ, PAGE_SIZE) < 0)
> 
> I suppose I /did/ say during LSFMM that for the current users of xfile.c
> and xfs_buf_mem.c the order of the folio being returned doesn't really
I not sure if I understood you well. Could you please elaborate on this?

> matter, but why wouldn't the last argument here be "roundup_64(count,
> PAGE_SIZE)" ?  Shouldn't we at least hint to the page cache about the
> folio order that we actually want instead of limiting it to order-0?

For v2, I'll include your suggestions. I think we can also enable large folios
in xfile_get_folio(), please check below:

diff --git a/fs/xfs/scrub/xfile.c b/fs/xfs/scrub/xfile.c
index 8cdd863db585..df8b495b4939 100644
--- a/fs/xfs/scrub/xfile.c
+++ b/fs/xfs/scrub/xfile.c
@@ -127,7 +127,7 @@ xfile_load(
                unsigned int    offset;

                if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
-                               SGP_READ) < 0)
+                               SGP_READ, roundup_64(count, PAGE_SIZE)) < 0)
                        break;
                if (!folio) {
                        /*
@@ -197,7 +197,7 @@ xfile_store(
                unsigned int    offset;

                if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
-                               SGP_CACHE) < 0)
+                               SGP_CACHE, roundup_64(count, PAGE_SIZE)) < 0)
                        break;
                if (filemap_check_wb_err(inode->i_mapping, 0)) {
                        folio_unlock(folio);
@@ -268,7 +268,8 @@ xfile_get_folio(

        pflags = memalloc_nofs_save();
        error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
-                       (flags & XFILE_ALLOC) ? SGP_CACHE : SGP_READ);
+                       (flags & XFILE_ALLOC) ? SGP_CACHE : SGP_READ,
+                       roundup_64(i_size_read(inode), PAGE_SIZE));
        memalloc_nofs_restore(pflags);
        if (error)
                return ERR_PTR(error);

> 
> (Also it seems a little odd to me that the @index is in units of pgoff_t
> but @len is in bytes.)

I extended the shmem_get_folio() with @len to calculate folio order based on
size (bytes). This is sent to ilog2() although I'm planning to use get_order()
instead (after fixing the issues mentioned during the discussion). @index is
used for __ffs() (same as in filemap).

Would you use lofft for @len instead? Or what's your suggestion?

Thanks,
Daniel

> 
> >  			break;
> >  		if (!folio) {
> >  			/*
> > @@ -197,7 +197,7 @@ xfile_store(
> >  		unsigned int	offset;
> >  
> >  		if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
> > -				SGP_CACHE) < 0)
> > +				SGP_CACHE, PAGE_SIZE) < 0)
> >  			break;
> >  		if (filemap_check_wb_err(inode->i_mapping, 0)) {
> >  			folio_unlock(folio);
> > @@ -268,7 +268,7 @@ xfile_get_folio(
> >  
> >  	pflags = memalloc_nofs_save();
> >  	error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
> > -			(flags & XFILE_ALLOC) ? SGP_CACHE : SGP_READ);
> > +			(flags & XFILE_ALLOC) ? SGP_CACHE : SGP_READ, PAGE_SIZE);
> >  	memalloc_nofs_restore(pflags);
> >  	if (error)
> >  		return ERR_PTR(error);
> > diff --git a/fs/xfs/xfs_buf_mem.c b/fs/xfs/xfs_buf_mem.c
> > index 9bb2d24de709..784c81d35a1f 100644
> > --- a/fs/xfs/xfs_buf_mem.c
> > +++ b/fs/xfs/xfs_buf_mem.c
> > @@ -149,7 +149,8 @@ xmbuf_map_page(
> >  		return -ENOMEM;
> >  	}
> >  
> > -	error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio, SGP_CACHE);
> > +	error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio, SGP_CACHE,
> > +				PAGE_SIZE);
> 
> This is ok unless someone wants to use a different XMBUF_BLOCKSIZE.
> 
> --D
> 
> >  	if (error)
> >  		return error;
> >  
> > diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> > index 3fb18f7eb73e..bc59b4a00228 100644
> > --- a/include/linux/shmem_fs.h
> > +++ b/include/linux/shmem_fs.h
> > @@ -142,7 +142,7 @@ enum sgp_type {
> >  };
> >  
> >  int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop,
> > -		enum sgp_type sgp);
> > +		enum sgp_type sgp, size_t len);
> >  struct folio *shmem_read_folio_gfp(struct address_space *mapping,
> >  		pgoff_t index, gfp_t gfp);
> >  
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 38830174608f..947770ded68c 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -1863,7 +1863,8 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> >  				xas_unlock_irq(&xas);
> >  				/* swap in or instantiate fallocated page */
> >  				if (shmem_get_folio(mapping->host, index,
> > -						&folio, SGP_NOALLOC)) {
> > +						    &folio, SGP_NOALLOC,
> > +						    PAGE_SIZE)) {
> >  					result = SCAN_FAIL;
> >  					goto xa_unlocked;
> >  				}
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > index d531018ffece..fcd2c9befe19 100644
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -1134,7 +1134,7 @@ static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
> >  	 * (although in some cases this is just a waste of time).
> >  	 */
> >  	folio = NULL;
> > -	shmem_get_folio(inode, index, &folio, SGP_READ);
> > +	shmem_get_folio(inode, index, &folio, SGP_READ, PAGE_SIZE);
> >  	return folio;
> >  }
> >  
> > @@ -1844,7 +1844,7 @@ static struct folio *shmem_alloc_folio(gfp_t gfp, struct shmem_inode_info *info,
> >  
> >  static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
> >  		struct inode *inode, pgoff_t index,
> > -		struct mm_struct *fault_mm, bool huge)
> > +		struct mm_struct *fault_mm, bool huge, size_t len)
> >  {
> >  	struct address_space *mapping = inode->i_mapping;
> >  	struct shmem_inode_info *info = SHMEM_I(inode);
> > @@ -2173,7 +2173,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
> >   */
> >  static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
> >  		struct folio **foliop, enum sgp_type sgp, gfp_t gfp,
> > -		struct vm_fault *vmf, vm_fault_t *fault_type)
> > +		struct vm_fault *vmf, vm_fault_t *fault_type, size_t len)
> >  {
> >  	struct vm_area_struct *vma = vmf ? vmf->vma : NULL;
> >  	struct mm_struct *fault_mm;
> > @@ -2258,7 +2258,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
> >  		huge_gfp = vma_thp_gfp_mask(vma);
> >  		huge_gfp = limit_gfp_mask(huge_gfp, gfp);
> >  		folio = shmem_alloc_and_add_folio(huge_gfp,
> > -				inode, index, fault_mm, true);
> > +				inode, index, fault_mm, true, len);
> >  		if (!IS_ERR(folio)) {
> >  			count_vm_event(THP_FILE_ALLOC);
> >  			goto alloced;
> > @@ -2267,7 +2267,8 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
> >  			goto repeat;
> >  	}
> >  
> > -	folio = shmem_alloc_and_add_folio(gfp, inode, index, fault_mm, false);
> > +	folio = shmem_alloc_and_add_folio(gfp, inode, index, fault_mm, false,
> > +					  len);
> >  	if (IS_ERR(folio)) {
> >  		error = PTR_ERR(folio);
> >  		if (error == -EEXIST)
> > @@ -2377,10 +2378,10 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
> >   * Return: 0 if successful, else a negative error code.
> >   */
> >  int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop,
> > -		enum sgp_type sgp)
> > +		enum sgp_type sgp, size_t len)
> >  {
> >  	return shmem_get_folio_gfp(inode, index, foliop, sgp,
> > -			mapping_gfp_mask(inode->i_mapping), NULL, NULL);
> > +			mapping_gfp_mask(inode->i_mapping), NULL, NULL, len);
> >  }
> >  EXPORT_SYMBOL_GPL(shmem_get_folio);
> >  
> > @@ -2475,7 +2476,7 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
> >  
> >  	WARN_ON_ONCE(vmf->page != NULL);
> >  	err = shmem_get_folio_gfp(inode, vmf->pgoff, &folio, SGP_CACHE,
> > -				  gfp, vmf, &ret);
> > +				  gfp, vmf, &ret, PAGE_SIZE);
> >  	if (err)
> >  		return vmf_error(err);
> >  	if (folio) {
> > @@ -2954,6 +2955,9 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
> >  	struct folio *folio;
> >  	int ret = 0;
> >  
> > +	if (!mapping_large_folio_support(mapping))
> > +		len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
> > +
> >  	/* i_rwsem is held by caller */
> >  	if (unlikely(info->seals & (F_SEAL_GROW |
> >  				   F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
> > @@ -2963,7 +2967,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
> >  			return -EPERM;
> >  	}
> >  
> > -	ret = shmem_get_folio(inode, index, &folio, SGP_WRITE);
> > +	ret = shmem_get_folio(inode, index, &folio, SGP_WRITE, len);
> >  	if (ret)
> >  		return ret;
> >  
> > @@ -3083,7 +3087,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> >  				break;
> >  		}
> >  
> > -		error = shmem_get_folio(inode, index, &folio, SGP_READ);
> > +		error = shmem_get_folio(inode, index, &folio, SGP_READ, PAGE_SIZE);
> >  		if (error) {
> >  			if (error == -EINVAL)
> >  				error = 0;
> > @@ -3260,7 +3264,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
> >  			break;
> >  
> >  		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio,
> > -					SGP_READ);
> > +					SGP_READ, PAGE_SIZE);
> >  		if (error) {
> >  			if (error == -EINVAL)
> >  				error = 0;
> > @@ -3469,7 +3473,8 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
> >  			error = -ENOMEM;
> >  		else
> >  			error = shmem_get_folio(inode, index, &folio,
> > -						SGP_FALLOC);
> > +						SGP_FALLOC,
> > +						(end - index) << PAGE_SHIFT);
> >  		if (error) {
> >  			info->fallocend = undo_fallocend;
> >  			/* Remove the !uptodate folios we added */
> > @@ -3822,7 +3827,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
> >  	} else {
> >  		inode_nohighmem(inode);
> >  		inode->i_mapping->a_ops = &shmem_aops;
> > -		error = shmem_get_folio(inode, 0, &folio, SGP_WRITE);
> > +		error = shmem_get_folio(inode, 0, &folio, SGP_WRITE, PAGE_SIZE);
> >  		if (error)
> >  			goto out_remove_offset;
> >  		inode->i_op = &shmem_symlink_inode_operations;
> > @@ -3868,7 +3873,7 @@ static const char *shmem_get_link(struct dentry *dentry, struct inode *inode,
> >  			return ERR_PTR(-ECHILD);
> >  		}
> >  	} else {
> > -		error = shmem_get_folio(inode, 0, &folio, SGP_READ);
> > +		error = shmem_get_folio(inode, 0, &folio, SGP_READ, PAGE_SIZE);
> >  		if (error)
> >  			return ERR_PTR(error);
> >  		if (!folio)
> > @@ -5255,7 +5260,7 @@ struct folio *shmem_read_folio_gfp(struct address_space *mapping,
> >  	int error;
> >  
> >  	error = shmem_get_folio_gfp(inode, index, &folio, SGP_CACHE,
> > -				    gfp, NULL, NULL);
> > +				    gfp, NULL, NULL, PAGE_SIZE);
> >  	if (error)
> >  		return ERR_PTR(error);
> >  
> > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> > index 3c3539c573e7..540a0c2d4325 100644
> > --- a/mm/userfaultfd.c
> > +++ b/mm/userfaultfd.c
> > @@ -359,7 +359,7 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
> >  	struct page *page;
> >  	int ret;
> >  
> > -	ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC);
> > +	ret = shmem_get_folio(inode, pgoff, &folio, SGP_NOALLOC, PAGE_SIZE);
> >  	/* Our caller expects us to return -EFAULT if we failed to find folio */
> >  	if (ret == -ENOENT)
> >  		ret = -EFAULT;
> > -- 
> > 2.43.0
> > 

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