[V4 PATCH 1/2] tmpfs: add fallocate support

[V4 PATCH 1/2] tmpfs: add fallocate support

[Cong Wang]

Systemd needs tmpfs to support fallocate [1], to be able
to safely use mmap(), regarding SIGBUS, on files on the
/dev/shm filesystem. The glibc fallback loop for -ENOSYS
on fallocate is just ugly.

This patch adds fallocate support to tmpfs, and as we
already have shmem_truncate_range(), it is also easy to
add FALLOC_FL_PUNCH_HOLE support too.

1. http://lkml.org/lkml/2011/10/20/275

V3->V4:
Handle 'undo' ENOSPC more correctly.

V2->V3:
a) Read i_size directly after holding i_mutex;
b) Call page_cache_release() too after shmem_getpage();
c) Undo previous changes when -ENOSPC.

Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: WANG Cong <amwang@redhat.com>

---
 mm/shmem.c |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 90 insertions(+), 0 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index d672250..90c835b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -30,6 +30,7 @@
 #include <linux/mm.h>
 #include <linux/export.h>
 #include <linux/swap.h>
+#include <linux/falloc.h>
 
 static struct vfsmount *shm_mnt;
 
@@ -1016,6 +1017,35 @@ failed:
 	return error;
 }
 
+static void shmem_putpage_noswap(struct inode *inode, pgoff_t index)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct shmem_inode_info *info;
+	struct shmem_sb_info *sbinfo;
+	struct page *page;
+
+	page = find_lock_page(mapping, index);
+
+	if (page) {
+		info = SHMEM_I(inode);
+		sbinfo = SHMEM_SB(inode->i_sb);
+		shmem_acct_block(info->flags);
+		if (PageDirty(page)) {
+			ClearPageDirty(page);
+			delete_from_page_cache(page);
+			spin_lock(&info->lock);
+			info->alloced--;
+			inode->i_blocks -= BLOCKS_PER_PAGE;
+			spin_unlock(&info->lock);
+		}
+		if (sbinfo->max_blocks)
+			percpu_counter_add(&sbinfo->used_blocks, -1);
+		shmem_unacct_blocks(info->flags, 1);
+		unlock_page(page);
+		page_cache_release(page);
+	}
+}
+
 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
@@ -1431,6 +1461,65 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
 	return error;
 }
 
+static long shmem_fallocate(struct file *file, int mode,
+				loff_t offset, loff_t len)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	pgoff_t start = offset >> PAGE_CACHE_SHIFT;
+	pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
+	pgoff_t index = start;
+	loff_t i_size;
+	struct page *page = NULL;
+	int ret = 0;
+
+	if (IS_SWAPFILE(inode))
+		return -ETXTBSY;
+
+	mutex_lock(&inode->i_mutex);
+	i_size = inode->i_size;
+	if (mode & FALLOC_FL_PUNCH_HOLE) {
+		if (!(offset > i_size || (end << PAGE_CACHE_SHIFT) > i_size))
+			shmem_truncate_range(inode, offset,
+					     (end << PAGE_CACHE_SHIFT) - 1);
+		goto unlock;
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+		ret = inode_newsize_ok(inode, (offset + len));
+		if (ret)
+			goto unlock;
+	}
+
+	while (index < end) {
+		ret = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
+		if (ret) {
+			if (ret == -ENOSPC)
+				goto undo;
+			else
+				goto unlock;
+		}
+		if (page) {
+			unlock_page(page);
+			page_cache_release(page);
+		}
+		index++;
+	}
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size)
+		i_size_write(inode, index << PAGE_CACHE_SHIFT);
+
+	goto unlock;
+
+undo:
+	while (index > start) {
+		shmem_putpage_noswap(inode, index);
+		index--;
+	}
+
+unlock:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
@@ -2286,6 +2375,7 @@ static const struct file_operations shmem_file_operations = {
 	.fsync		= noop_fsync,
 	.splice_read	= shmem_file_splice_read,
 	.splice_write	= generic_file_splice_write,
+	.fallocate	= shmem_fallocate,
 #endif
 };
 

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[V2 PATCH 2/2] fs: wire up .truncate_range and .fallocate

[Cong Wang]

V1->V2:
Move tmpfs stuff into shmem_fallocate(), suggested by Christoph.

As Hugh suggested, with FALLOC_FL_PUNCH_HOLE, we can use do_fallocate()
to implement madvise_remove and finally remove .truncate_range call back.

Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: WANG Cong <amwang@redhat.com>

---
 include/linux/fs.h |    1 -
 include/linux/mm.h |    2 +-
 mm/madvise.c       |    6 +++---
 mm/shmem.c         |   12 +++++++++++-
 mm/truncate.c      |   22 +++++-----------------
 5 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e313022..266df73 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1635,7 +1635,6 @@ struct inode_operations {
 	ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
 	int (*removexattr) (struct dentry *, const char *);
-	void (*truncate_range)(struct inode *, loff_t, loff_t);
 	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
 		      u64 len);
 } ____cacheline_aligned;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3dc3a8c..0582ce8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -951,7 +951,7 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping,
 extern void truncate_pagecache(struct inode *inode, loff_t old, loff_t new);
 extern void truncate_setsize(struct inode *inode, loff_t newsize);
 extern int vmtruncate(struct inode *inode, loff_t offset);
-extern int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end);
+extern int vmtruncate_file_range(struct file *file, loff_t offset, loff_t end);
 
 int truncate_inode_page(struct address_space *mapping, struct page *page);
 int generic_error_remove_page(struct address_space *mapping, struct page *page);
diff --git a/mm/madvise.c b/mm/madvise.c
index 74bf193..3a281b7 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -194,7 +194,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 				struct vm_area_struct **prev,
 				unsigned long start, unsigned long end)
 {
-	struct address_space *mapping;
+	struct file *file;
 	loff_t offset, endoff;
 	int error;
 
@@ -211,7 +211,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 	if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 		return -EACCES;
 
-	mapping = vma->vm_file->f_mapping;
+	file = vma->vm_file;
 
 	offset = (loff_t)(start - vma->vm_start)
 			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
@@ -220,7 +220,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 
 	/* vmtruncate_range needs to take i_mutex */
 	up_read(&current->mm->mmap_sem);
-	error = vmtruncate_range(mapping->host, offset, endoff);
+	error = vmtruncate_file_range(file, offset, endoff);
 	down_read(&current->mm->mmap_sem);
 	return error;
 }
diff --git a/mm/shmem.c b/mm/shmem.c
index 90c835b..b435da8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1465,6 +1465,7 @@ static long shmem_fallocate(struct file *file, int mode,
 				loff_t offset, loff_t len)
 {
 	struct inode *inode = file->f_path.dentry->d_inode;
+	struct address_space *mapping = file->f_mapping;
 	pgoff_t start = offset >> PAGE_CACHE_SHIFT;
 	pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
 	pgoff_t index = start;
@@ -1476,6 +1477,12 @@ static long shmem_fallocate(struct file *file, int mode,
 		return -ETXTBSY;
 
 	mutex_lock(&inode->i_mutex);
+
+	if (mapping) {
+		inode_dio_wait(mapping->host);
+		unmap_mapping_range(mapping, offset, len, 1);
+	}
+
 	i_size = inode->i_size;
 	if (mode & FALLOC_FL_PUNCH_HOLE) {
 		if (!(offset > i_size || (end << PAGE_CACHE_SHIFT) > i_size))
@@ -1507,6 +1514,10 @@ static long shmem_fallocate(struct file *file, int mode,
 	if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size)
 		i_size_write(inode, index << PAGE_CACHE_SHIFT);
 
+	/* unmap again to remove racily COWed private pages */
+	if (mapping)
+		unmap_mapping_range(mapping, offset, len, 1);
+
 	goto unlock;
 
 undo:
@@ -2381,7 +2392,6 @@ static const struct file_operations shmem_file_operations = {
 
 static const struct inode_operations shmem_inode_operations = {
 	.setattr	= shmem_setattr,
-	.truncate_range	= shmem_truncate_range,
 #ifdef CONFIG_TMPFS_XATTR
 	.setxattr	= shmem_setxattr,
 	.getxattr	= shmem_getxattr,
diff --git a/mm/truncate.c b/mm/truncate.c
index 632b15e..5a7ddda 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -20,6 +20,7 @@
 #include <linux/buffer_head.h>	/* grr. try_to_release_page,
 				   do_invalidatepage */
 #include <linux/cleancache.h>
+#include <linux/falloc.h>
 #include "internal.h"
 
 
@@ -602,27 +603,14 @@ int vmtruncate(struct inode *inode, loff_t newsize)
 }
 EXPORT_SYMBOL(vmtruncate);
 
-int vmtruncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+int vmtruncate_file_range(struct file *file, loff_t lstart, loff_t lend)
 {
-	struct address_space *mapping = inode->i_mapping;
 	loff_t holebegin = round_up(lstart, PAGE_SIZE);
 	loff_t holelen = 1 + lend - holebegin;
 
-	/*
-	 * If the underlying filesystem is not going to provide
-	 * a way to truncate a range of blocks (punch a hole) -
-	 * we should return failure right now.
-	 */
-	if (!inode->i_op->truncate_range)
+	if (!file->f_op->fallocate)
 		return -ENOSYS;
 
-	mutex_lock(&inode->i_mutex);
-	inode_dio_wait(inode);
-	unmap_mapping_range(mapping, holebegin, holelen, 1);
-	inode->i_op->truncate_range(inode, lstart, lend);
-	/* unmap again to remove racily COWed private pages */
-	unmap_mapping_range(mapping, holebegin, holelen, 1);
-	mutex_unlock(&inode->i_mutex);
-
-	return 0;
+	return do_fallocate(file, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE,
+		     holebegin, holelen);
 }

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Re: [V4 PATCH 1/2] tmpfs: add fallocate support

[KAMEZAWA Hiroyuki]

On Tue, 29 Nov 2011 13:33:12 +0800
Cong Wang <amwang@redhat.com> wrote:

> Systemd needs tmpfs to support fallocate [1], to be able
> to safely use mmap(), regarding SIGBUS, on files on the
> /dev/shm filesystem. The glibc fallback loop for -ENOSYS
> on fallocate is just ugly.
> 
> This patch adds fallocate support to tmpfs, and as we
> already have shmem_truncate_range(), it is also easy to
> add FALLOC_FL_PUNCH_HOLE support too.
> 
> 1. http://lkml.org/lkml/2011/10/20/275
> 

one question.


> V3->V4:
> Handle 'undo' ENOSPC more correctly.
> 
> V2->V3:
> a) Read i_size directly after holding i_mutex;
> b) Call page_cache_release() too after shmem_getpage();
> c) Undo previous changes when -ENOSPC.
> 
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> Cc: Lennart Poettering <lennart@poettering.net>
> Cc: Kay Sievers <kay.sievers@vrfy.org>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: WANG Cong <amwang@redhat.com>
> 
> ---
>  mm/shmem.c |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 90 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d672250..90c835b 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -30,6 +30,7 @@
>  #include <linux/mm.h>
>  #include <linux/export.h>
>  #include <linux/swap.h>
> +#include <linux/falloc.h>
>  
>  static struct vfsmount *shm_mnt;
>  
> @@ -1016,6 +1017,35 @@ failed:
>  	return error;
>  }
>  
> +static void shmem_putpage_noswap(struct inode *inode, pgoff_t index)
> +{
> +	struct address_space *mapping = inode->i_mapping;
> +	struct shmem_inode_info *info;
> +	struct shmem_sb_info *sbinfo;
> +	struct page *page;
> +
> +	page = find_lock_page(mapping, index);
> +

You can't know whether the 'page' is allocated by alloc_page() in fallocate()
or just found as exiting one.
Then, yourwill corrupt existing pages in error path.
Is it allowed ?

Thanks,
-Kame

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Re: [V4 PATCH 1/2] tmpfs: add fallocate support

[Cong Wang]

[-- Attachment #1: Type: text/plain, Size: 774 bytes --]

ao? 2011a1'11ae??29ae?JPY 14:02, KAMEZAWA Hiroyuki a??e??:
>
> You can't know whether the 'page' is allocated by alloc_page() in fallocate()
> or just found as exiting one.
> Then, yourwill corrupt existing pages in error path.
> Is it allowed ?
>

According to the comment,

/*
  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
  *
  * If we allocate a new one we do not mark it dirty. That's up to the
  * vm. If we swap it in we mark it dirty since we also free the swap
  * entry since a page cannot live in both the swap and page cache
  */

so we can know if the page is newly allocated by checking page dirty bit.
Or am I missing something?

But whoops, I sent a wrong version of this patch, the below one is
the correct one. Sorry for this.


[-- Attachment #2: 0001-tmpfs-add-fallocate-support.patch --]
[-- Type: text/plain, Size: 4320 bytes --]

Subject: [V4 PATCH 1/2] tmpfs: add fallocate support

Systemd needs tmpfs to support fallocate [1], to be able
to safely use mmap(), regarding SIGBUS, on files on the
/dev/shm filesystem. The glibc fallback loop for -ENOSYS
on fallocate is just ugly.

This patch adds fallocate support to tmpfs, and as we
already have shmem_truncate_range(), it is also easy to
add FALLOC_FL_PUNCH_HOLE support too.

1. http://lkml.org/lkml/2011/10/20/275

V3->V4:
Handle 'undo' ENOSPC more correctly.

V2->V3:
a) Read i_size directly after holding i_mutex;
b) Call page_cache_release() too after shmem_getpage();
c) Undo previous changes when -ENOSPC.

Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: WANG Cong <amwang@redhat.com>

---
commit ca055ad343a0d629f8f1fad1df30796d2292f6a2
Author: Cong Wang <amwang@redhat.com>
Date:   Wed Nov 23 13:16:26 2011 +0800

    tmpfs: add fallocate support
---
 mm/shmem.c |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 90 insertions(+), 0 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index d672250..6a6fc66 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -30,6 +30,7 @@
 #include <linux/mm.h>
 #include <linux/export.h>
 #include <linux/swap.h>
+#include <linux/falloc.h>
 
 static struct vfsmount *shm_mnt;
 
@@ -1016,6 +1017,35 @@ failed:
 	return error;
 }
 
+static void shmem_putpage_noswap(struct inode *inode, pgoff_t index, bool new)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct shmem_inode_info *info;
+	struct shmem_sb_info *sbinfo;
+	struct page *page;
+
+	page = find_lock_page(mapping, index);
+
+	if (page) {
+		info = SHMEM_I(inode);
+		sbinfo = SHMEM_SB(inode->i_sb);
+		shmem_acct_block(info->flags);
+		if (!new && PageDirty(page)) {
+			ClearPageDirty(page);
+			delete_from_page_cache(page);
+			spin_lock(&info->lock);
+			info->alloced--;
+			inode->i_blocks -= BLOCKS_PER_PAGE;
+			spin_unlock(&info->lock);
+		}
+		if (sbinfo->max_blocks)
+			percpu_counter_add(&sbinfo->used_blocks, -1);
+		shmem_unacct_blocks(info->flags, 1);
+		unlock_page(page);
+		page_cache_release(page);
+	}
+}
+
 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
@@ -1431,6 +1461,65 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
 	return error;
 }
 
+static long shmem_fallocate(struct file *file, int mode,
+				loff_t offset, loff_t len)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	pgoff_t start = offset >> PAGE_CACHE_SHIFT;
+	pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
+	pgoff_t index = start;
+	loff_t i_size;
+	struct page *page = NULL;
+	int ret = 0;
+
+	if (IS_SWAPFILE(inode))
+		return -ETXTBSY;
+
+	mutex_lock(&inode->i_mutex);
+	i_size = inode->i_size;
+	if (mode & FALLOC_FL_PUNCH_HOLE) {
+		if (!(offset > i_size || (end << PAGE_CACHE_SHIFT) > i_size))
+			shmem_truncate_range(inode, offset,
+					     (end << PAGE_CACHE_SHIFT) - 1);
+		goto unlock;
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+		ret = inode_newsize_ok(inode, (offset + len));
+		if (ret)
+			goto unlock;
+	}
+
+	while (index < end) {
+		ret = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
+		if (ret) {
+			if (ret == -ENOSPC)
+				goto undo;
+			else
+				goto unlock;
+		}
+		if (page) {
+			unlock_page(page);
+			page_cache_release(page);
+		}
+		index++;
+	}
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size)
+		i_size_write(inode, index << PAGE_CACHE_SHIFT);
+
+	goto unlock;
+
+undo:
+	while (index > start) {
+		shmem_putpage_noswap(inode, index, true);
+		index--;
+	}
+
+unlock:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
@@ -2286,6 +2375,7 @@ static const struct file_operations shmem_file_operations = {
 	.fsync		= noop_fsync,
 	.splice_read	= shmem_file_splice_read,
 	.splice_write	= generic_file_splice_write,
+	.fallocate	= shmem_fallocate,
 #endif
 };
 

Re: [V4 PATCH 1/2] tmpfs: add fallocate support

[KAMEZAWA Hiroyuki]

On Tue, 29 Nov 2011 15:23:58 +0800
Cong Wang <amwang@redhat.com> wrote:

> 于 2011年11月29日 14:02, KAMEZAWA Hiroyuki 写道:
> >
> > You can't know whether the 'page' is allocated by alloc_page() in fallocate()
> > or just found as exiting one.
> > Then, yourwill corrupt existing pages in error path.
> > Is it allowed ?
> >
> 
> According to the comment,
> 
> /*
>   * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
>   *
>   * If we allocate a new one we do not mark it dirty. That's up to the
>   * vm. If we swap it in we mark it dirty since we also free the swap
>   * entry since a page cannot live in both the swap and page cache
>   */
> 
> so we can know if the page is newly allocated by checking page dirty bit.
> Or am I missing something?
> 

If swap-in doesn't happen and  a page is found...

==
       page = find_lock_page(mapping, index); <=============== you find a page
       if (radix_tree_exceptional_entry(page)) {
                swap = radix_to_swp_entry(page);
                page = NULL;
        }

        if (sgp != SGP_WRITE &&
            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
                error = -EINVAL;
                goto failed;
        }

        if (page || (sgp == SGP_READ && !swap.val)) {
                /*
                 * Once we can get the page lock, it must be uptodate:
                 * if there were an error in reading back from swap,
                 * the page would not be inserted into the filecache.
                 */
                BUG_ON(page && !PageUptodate(page));
                *pagep = page; <========================= return here.
                return 0;
        }
==
Page will not be marked as dirty.

Thanks,
-Kame

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