[PATCH v1 0/5] Enable holes on copy_file_range()

[PATCH v1 0/5] Enable holes on copy_file_range()

[Goldwyn Rodrigues]

If copy_file_range performs a copy using splice, it converts holes
to zeros. This effort primarily changes this behavior to create
holes when it is possible. 

Even if copy_file_range() or clone_file_range() does not work for different
mounted filesystems, We should be able to splice files if they do not
belong the same super_block.

Changes since v0:
- [Amir] Carved out do_copy_file_range() which can be used by overlayfs

-- 
Goldwyn

[PATCH 1/4] copy_file_range: refactor vfs_copy_file_range

[Goldwyn Rodrigues]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Preparatory patch to carve out do_copy_file_range() from
vfs_copy_file_range

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/read_write.c | 67 ++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 38 insertions(+), 29 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index c4eabbfc90df..7d9dfb62ba7d 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1541,6 +1541,42 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
 }
 #endif
 
+ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
+			    struct file *file_out, loff_t pos_out,
+			    size_t len, unsigned int flags,
+			    unsigned int splice_flags)
+{
+	ssize_t ret = 0;
+
+	if (flags != 0)
+		return -EINVAL;
+
+	if (len == 0)
+		return 0;
+
+	/*
+	 * Try cloning first, this is supported by more file systems, and
+	 * more efficient if both clone and copy are supported (e.g. NFS).
+	 */
+	if (file_in->f_op->clone_file_range) {
+		ret = file_in->f_op->clone_file_range(file_in, pos_in,
+				file_out, pos_out, len);
+		if (ret == 0)
+			return len;
+	}
+
+	if (file_out->f_op->copy_file_range) {
+		ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out,
+						      pos_out, len, flags);
+		if (ret != -EOPNOTSUPP)
+			return ret;
+	}
+
+	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
+			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, splice_flags);
+	return ret;
+}
+
 /*
  * copy_file_range() differs from regular file read and write in that it
  * specifically allows return partial success.  When it does so is up to
@@ -1554,9 +1590,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	struct inode *inode_out = file_inode(file_out);
 	ssize_t ret;
 
-	if (flags != 0)
-		return -EINVAL;
-
 	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
 		return -EISDIR;
 	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
@@ -1579,35 +1612,11 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	if (inode_in->i_sb != inode_out->i_sb)
 		return -EXDEV;
 
-	if (len == 0)
-		return 0;
-
 	file_start_write(file_out);
 
-	/*
-	 * Try cloning first, this is supported by more file systems, and
-	 * more efficient if both clone and copy are supported (e.g. NFS).
-	 */
-	if (file_in->f_op->clone_file_range) {
-		ret = file_in->f_op->clone_file_range(file_in, pos_in,
-				file_out, pos_out, len);
-		if (ret == 0) {
-			ret = len;
-			goto done;
-		}
-	}
-
-	if (file_out->f_op->copy_file_range) {
-		ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out,
-						      pos_out, len, flags);
-		if (ret != -EOPNOTSUPP)
-			goto done;
-	}
-
-	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
-			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
+	ret = do_copy_file_range(file_in, pos_in,
+			file_out, pos_out, len, flags, 0);
 
-done:
 	if (ret > 0) {
 		fsnotify_access(file_in);
 		add_rchar(current, ret);
-- 
2.16.3

[PATCH 2/4] copy_file_range: Perform splice if in/out SB are not same

[Goldwyn Rodrigues]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

While performing copy_file_range(), if superblocks of file_in and
file_out don't match, instead of returning -EXDEV, perform
splice for a faster copy.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/read_write.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 7d9dfb62ba7d..2c9e7a5ea806 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1546,6 +1546,8 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 			    size_t len, unsigned int flags,
 			    unsigned int splice_flags)
 {
+	struct inode *inode_in = file_inode(file_in);
+	struct inode *inode_out = file_inode(file_out);
 	ssize_t ret = 0;
 
 	if (flags != 0)
@@ -1554,6 +1556,9 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 	if (len == 0)
 		return 0;
 
+	if (inode_in->i_sb != inode_out->i_sb)
+		goto splice;
+
 	/*
 	 * Try cloning first, this is supported by more file systems, and
 	 * more efficient if both clone and copy are supported (e.g. NFS).
@@ -1571,7 +1576,7 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 		if (ret != -EOPNOTSUPP)
 			return ret;
 	}
-
+splice:
 	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
 			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, splice_flags);
 	return ret;
@@ -1608,10 +1613,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	    (file_out->f_flags & O_APPEND))
 		return -EBADF;
 
-	/* this could be relaxed once a method supports cross-fs copies */
-	if (inode_in->i_sb != inode_out->i_sb)
-		return -EXDEV;
-
 	file_start_write(file_out);
 
 	ret = do_copy_file_range(file_in, pos_in,
-- 
2.16.3

Re: [PATCH 2/4] copy_file_range: Perform splice if in/out SB are not same

[Florian Weimer]

On 05/08/2018 11:24 PM, Goldwyn Rodrigues wrote:
> While performing copy_file_range(), if superblocks of file_in and
> file_out don't match, instead of returning -EXDEV, perform
> splice for a faster copy.

We have a userspace emulation in glibc which used to be quite faithful, 
including the EXDEV error (which is not strictly necessary to produce).

Should we change glibc to perform a userspace copy if the system call 
returns EXDEV due to an older kernel?

Thanks,
Florian

Re: [PATCH 2/4] copy_file_range: Perform splice if in/out SB are not same

[Goldwyn Rodrigues]

On 05/08/2018 04:57 PM, Florian Weimer wrote:
> On 05/08/2018 11:24 PM, Goldwyn Rodrigues wrote:
>> While performing copy_file_range(), if superblocks of file_in and
>> file_out don't match, instead of returning -EXDEV, perform
>> splice for a faster copy.
> 
> We have a userspace emulation in glibc which used to be quite faithful,
> including the EXDEV error (which is not strictly necessary to produce).
> 
> Should we change glibc to perform a userspace copy if the system call
> returns EXDEV due to an older kernel?
> 

I don't seen any purpose. The user would anyways have to perform a copy
if it receives -EXDEV.

-- 
Goldwyn

Re: [PATCH 2/4] copy_file_range: Perform splice if in/out SB are not same

[Amir Goldstein]

On Wed, May 9, 2018 at 12:24 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> While performing copy_file_range(), if superblocks of file_in and
> file_out don't match, instead of returning -EXDEV, perform
> splice for a faster copy.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
>  fs/read_write.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 7d9dfb62ba7d..2c9e7a5ea806 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1546,6 +1546,8 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
>                             size_t len, unsigned int flags,
>                             unsigned int splice_flags)
>  {
> +       struct inode *inode_in = file_inode(file_in);
> +       struct inode *inode_out = file_inode(file_out);
>         ssize_t ret = 0;
>
>         if (flags != 0)
> @@ -1554,6 +1556,9 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
>         if (len == 0)
>                 return 0;
>
> +       if (inode_in->i_sb != inode_out->i_sb)
> +               goto splice;
> +
>         /*
>          * Try cloning first, this is supported by more file systems, and
>          * more efficient if both clone and copy are supported (e.g. NFS).
> @@ -1571,7 +1576,7 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
>                 if (ret != -EOPNOTSUPP)
>                         return ret;
>         }
> -
> +splice:
>         ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
>                         len > MAX_RW_COUNT ? MAX_RW_COUNT : len, splice_flags);
>         return ret;
> @@ -1608,10 +1613,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
>             (file_out->f_flags & O_APPEND))
>                 return -EBADF;
>
> -       /* this could be relaxed once a method supports cross-fs copies */
> -       if (inode_in->i_sb != inode_out->i_sb)
> -               return -EXDEV;
> -
>         file_start_write(file_out);
>
>         ret = do_copy_file_range(file_in, pos_in,
> --
> 2.16.3
>
> --
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> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 3/4] copy_file_range: splice with holes

[Goldwyn Rodrigues]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

copy_file_range calls do_splice_direct() if fs->clone_file_range
or fs->copy_file_range() is not available. However, do_splice_direct()
converts holes to zeros. Detect holes in the file_in range, and
create them in the corresponding file_out range.

If there is already data present at the offset in file_out, attempt
to punch a hole there. If the operation is not supported, fall
back to performing splice on the whole range.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/read_write.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 55 insertions(+), 5 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 2c9e7a5ea806..5df9d6e8ebee 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -20,6 +20,7 @@
 #include <linux/compat.h>
 #include <linux/mount.h>
 #include <linux/fs.h>
+#include <linux/falloc.h>
 #include "internal.h"
 
 #include <linux/uaccess.h>
@@ -1541,14 +1542,15 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
 }
 #endif
 
-ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
+static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 			    struct file *file_out, loff_t pos_out,
 			    size_t len, unsigned int flags,
 			    unsigned int splice_flags)
 {
 	struct inode *inode_in = file_inode(file_in);
 	struct inode *inode_out = file_inode(file_out);
-	ssize_t ret = 0;
+	ssize_t ret = 0, total = 0;
+	loff_t size, end;
 
 	if (flags != 0)
 		return -EINVAL;
@@ -1576,10 +1578,58 @@ ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 		if (ret != -EOPNOTSUPP)
 			return ret;
 	}
+
 splice:
-	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
-			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, splice_flags);
-	return ret;
+	while (total < len) {
+		end = vfs_llseek(file_in, pos_in, SEEK_HOLE);
+
+		/* Starting position is already in a hole */
+		if (end == pos_in)
+			goto hole;
+		size = end - pos_in;
+do_splice:
+		ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
+				size, 0);
+		if (ret < 0)
+			goto out;
+		total += ret;
+		if (total == len)
+			break;
+hole:
+		end = vfs_llseek(file_in, pos_in, SEEK_DATA);
+		if (end < 0) {
+			ret = end;
+			goto out;
+		}
+		size = end - pos_in;
+		/* Data on offset, punch holes */
+		if (i_size_read(file_out->f_inode) > pos_out) {
+			ret = vfs_fallocate(file_out,
+					FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+					pos_out, size);
+			if (ret < 0) {
+				/*
+				 * The filesystem does not support punching
+				 * holes. Perform splice on the remaining range.
+				 */
+				if (ret == -EOPNOTSUPP) {
+					size = len - total;
+					goto do_splice;
+				}
+				goto out;
+			}
+		}
+		if (ret < 0) {
+			ret = end;
+			goto out;
+		}
+		pos_out += size;
+		pos_in = end;
+		total += size;
+	}
+
+out:
+	return total ? total : ret;
 }
 
 /*
-- 
2.16.3

Re: [PATCH 3/4] copy_file_range: splice with holes

[Florian Weimer]

On 05/08/2018 11:24 PM, Goldwyn Rodrigues wrote:
> copy_file_range calls do_splice_direct() if fs->clone_file_range
> or fs->copy_file_range() is not available. However, do_splice_direct()
> converts holes to zeros. Detect holes in the file_in range, and
> create them in the corresponding file_out range.

Should this be restricted to calls to copy_file_range with a 
(yet-to-be-defined) flag?

I was under the impression that the hole-filling nature of 
copy_file_range was not a bug.

Thanks,
Florian

Re: [PATCH 3/4] copy_file_range: splice with holes

[Dave Chinner]

On Tue, May 08, 2018 at 11:59:45PM +0200, Florian Weimer wrote:
> On 05/08/2018 11:24 PM, Goldwyn Rodrigues wrote:
> >copy_file_range calls do_splice_direct() if fs->clone_file_range
> >or fs->copy_file_range() is not available. However, do_splice_direct()
> >converts holes to zeros. Detect holes in the file_in range, and
> >create them in the corresponding file_out range.
> 
> Should this be restricted to calls to copy_file_range with a
> (yet-to-be-defined) flag?
> 
> I was under the impression that the hole-filling nature of
> copy_file_range was not a bug.

It's not a bug, but it's currently undefined behaviour. i.e. some
filesystem implementations will hole fill while others won't, and
you cannot predict ahead of time what will happen.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [PATCH 3/4] copy_file_range: splice with holes

[Amir Goldstein]

On Wed, May 9, 2018 at 12:24 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> copy_file_range calls do_splice_direct() if fs->clone_file_range
> or fs->copy_file_range() is not available. However, do_splice_direct()
> converts holes to zeros. Detect holes in the file_in range, and
> create them in the corresponding file_out range.
>
> If there is already data present at the offset in file_out, attempt
> to punch a hole there. If the operation is not supported, fall
> back to performing splice on the whole range.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

but..

> ---
>  fs/read_write.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 55 insertions(+), 5 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 2c9e7a5ea806..5df9d6e8ebee 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -20,6 +20,7 @@
>  #include <linux/compat.h>
>  #include <linux/mount.h>
>  #include <linux/fs.h>
> +#include <linux/falloc.h>
>  #include "internal.h"
>
>  #include <linux/uaccess.h>
> @@ -1541,14 +1542,15 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
>  }
>  #endif
>
> -ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
> +static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,

Either make it static to begin with or non static and exported to begin with.

Thanks,
Amir.

[PATCH 4/4] ovl: Use do_copy_file_range() in copy_up_data()

[Goldwyn Rodrigues]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

This will preserve the holes and will clone(), if available.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/overlayfs/copy_up.c | 28 ++++++++--------------------
 fs/read_write.c        |  3 ++-
 include/linux/fs.h     |  3 +++
 3 files changed, 13 insertions(+), 21 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 8bede0742619..1f89380873ce 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -138,8 +138,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 {
 	struct file *old_file;
 	struct file *new_file;
-	loff_t old_pos = 0;
-	loff_t new_pos = 0;
+	loff_t pos = 0;
 	int error = 0;
 
 	if (len == 0)
@@ -155,38 +154,27 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 		goto out_fput;
 	}
 
-	/* Try to use clone_file_range to clone up within the same fs */
-	error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
-	if (!error)
-		goto out;
-	/* Couldn't clone, so now we try to copy the data */
-	error = 0;
-
-	/* FIXME: copy up sparse files efficiently */
-	while (len) {
+	while (pos < len) {
 		size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
 		long bytes;
 
-		if (len < this_len)
-			this_len = len;
+		if (len - pos < this_len)
+			this_len = len - pos;
 
 		if (signal_pending_state(TASK_KILLABLE, current)) {
 			error = -EINTR;
 			break;
 		}
 
-		bytes = do_splice_direct(old_file, &old_pos,
-					 new_file, &new_pos,
-					 this_len, SPLICE_F_MOVE);
+		bytes = do_copy_file_range(old_file, pos,
+					 new_file, pos,
+					 this_len, 0, SPLICE_F_MOVE);
 		if (bytes <= 0) {
 			error = bytes;
 			break;
 		}
-		WARN_ON(old_pos != new_pos);
-
-		len -= bytes;
+		pos += bytes;
 	}
-out:
 	if (!error)
 		error = vfs_fsync(new_file, 0);
 	fput(new_file);
diff --git a/fs/read_write.c b/fs/read_write.c
index 5df9d6e8ebee..57b5b74c982a 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1542,7 +1542,7 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
 }
 #endif
 
-static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
+ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 			    struct file *file_out, loff_t pos_out,
 			    size_t len, unsigned int flags,
 			    unsigned int splice_flags)
@@ -1631,6 +1631,7 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
 out:
 	return total ? total : ret;
 }
+EXPORT_SYMBOL(do_copy_file_range);
 
 /*
  * copy_file_range() differs from regular file read and write in that it
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 760d8da1b6c7..d5349b17fa10 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1799,6 +1799,9 @@ extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
 extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
 		unsigned long, loff_t *, rwf_t);
+extern ssize_t do_copy_file_range(struct file *, loff_t , struct file *,
+				   loff_t , size_t, unsigned int,
+				   unsigned int);
 extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
 				   loff_t, size_t, unsigned int);
 extern int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
-- 
2.16.3

Re: [PATCH 4/4] ovl: Use do_copy_file_range() in copy_up_data()

[Amir Goldstein]

On Wed, May 9, 2018 at 12:24 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> This will preserve the holes and will clone(), if available.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

Only please mention in commit message that it changes behavoir
slightly for a very large file (clone in chunks).
I see no problem with this change.

And please test with xfstest overlay/001 with copies up a large
sparse file. test time should drop from ~30s to 0s.
If you like I can test that one for you.
I believe there are also generic copy_file_range tests in xfstests.

Thanks,
Amir.

Re: [PATCH 4/4] ovl: Use do_copy_file_range() in copy_up_data()

[Goldwyn Rodrigues]

On 05/09/2018 12:50 AM, Amir Goldstein wrote:
> On Wed, May 9, 2018 at 12:24 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
>> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>>
>> This will preserve the holes and will clone(), if available.
>>
>> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> 
> Only please mention in commit message that it changes behavoir
> slightly for a very large file (clone in chunks).

Change behavior? Only it will have holes. It will still respect length.
Actually, I found a bug when it would not respect length if offset is
father than length which I have fixed.

> I see no problem with this change.
> 
> And please test with xfstest overlay/001 with copies up a large
> sparse file. test time should drop from ~30s to 0s.

Yup, it passes in 1s on my VM :)

> If you like I can test that one for you.
> I believe there are also generic copy_file_range tests in xfstests.
> 

Thanks for the review

-- 
Goldwyn

Re: [PATCH 4/4] ovl: Use do_copy_file_range() in copy_up_data()

[Amir Goldstein]

On Wed, May 9, 2018 at 10:13 PM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
>
>
> On 05/09/2018 12:50 AM, Amir Goldstein wrote:
>> On Wed, May 9, 2018 at 12:24 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
>>> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>>>
>>> This will preserve the holes and will clone(), if available.
>>>
>>> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
>> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
>>
>> Only please mention in commit message that it changes behavoir
>> slightly for a very large file (clone in chunks).
>
> Change behavior? Only it will have holes. It will still respect length.
> Actually, I found a bug when it would not respect length if offset is
> father than length which I have fixed.

What I meant is the change of behavior for when underlying fs supports
clone.
Your patch changes the behavior for a very large file from single call
to vfs_clone_file_range() on entire length to several calls in a loop.

Nevermind. It's too insignificant for anyone to care.
If overlayfs ever supports NFS as upper layer, we may want to rethink
this.

Thanks,
Amir.