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Re: BTRFS file clone support for cp
From: |
Jim Meyering |
Subject: |
Re: BTRFS file clone support for cp |
Date: |
Fri, 07 Aug 2009 17:16:59 +0200 |
Giuseppe Scrivano wrote:
> Jim Meyering <address@hidden> writes:
>
>>> + if (clone_file (dest_desc, source_desc))
>>> + {
>>> + error (0, errno, _("cannot fstat %s"), quote (dst_name));
>>
>> I prefer this diagnostic ;-)
>>
>> error (0, errno, _("failed to clone %s"), quote (dst_name));
>
> Too wild copy&paste :)
>
> I included your notes in the following patch.
Thanks. I think this is finally ready.
Here are a few more small changes:
(alphabetize and change one-line description)
diff --git a/src/cp.c b/src/cp.c
index 635c7c7..ae1c1ce 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -192,11 +192,11 @@ Mandatory arguments to long options are mandatory for
short options too.\n\
"), stdout);
fputs (_("\
-R, -r, --recursive copy directories recursively\n\
+ --reflink perform a lightweight (CoW/clone) copy\n\
--remove-destination remove each existing destination file before\n\
attempting to open it (contrast with
--force)\n\
"), stdout);
fputs (_("\
- --reflink clone the file if it is possible\n\
--sparse=WHEN control creation of sparse files\n\
--strip-trailing-slashes remove any trailing slashes from each SOURCE\n\
argument\n\
I did the same with the addition of REFLINK_OPTION here:
enum
{
COPY_CONTENTS_OPTION = CHAR_MAX + 1,
NO_PRESERVE_ATTRIBUTES_OPTION,
PARENTS_OPTION,
PRESERVE_ATTRIBUTES_OPTION,
REFLINK_OPTION,
SPARSE_OPTION,
STRIP_TRAILING_SLASHES_OPTION,
UNLINK_DEST_BEFORE_OPENING
};
Plus, I adjusted the log message:
>From a1d7469835371ded0ad8e3496bc5a5bebf94ccef Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Sat, 1 Aug 2009 19:36:48 +0200
Subject: [PATCH] cp: accept the --reflink option
* NEWS: Mention it.
* doc/coreutils.texi (cp invocation): Describe it.
* src/copy.h (struct cp_options) [reflink]: New member.
* src/copy.c (usage): Describe it.
(copy_reg): If reflink is true try to clone the file.
(main): Check for --reflink.
(cp_option_init): Initialize the new member.
* src/install.c (cp_option_init): Initialize the new member.
* src/mv.c (cp_option_init): Likewise.
* tests/cp/sparse: Add a new test case.
---
NEWS | 4 ++++
doc/coreutils.texi | 9 +++++++++
src/copy.c | 16 ++++++++++------
src/copy.h | 3 +++
src/cp.c | 14 ++++++++++++++
src/install.c | 1 +
src/mv.c | 1 +
tests/cp/sparse | 4 ++++
8 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/NEWS b/NEWS
index c61f666..6df0d65 100644
--- a/NEWS
+++ b/NEWS
@@ -41,6 +41,10 @@ GNU coreutils NEWS -*-
outline -*-
chroot now accepts the options --userspec and --groups.
+ cp accepts a new option, --reflink: create a lightweight copy
+ using copy-on-write (COW). This is currently supported only on
+ btrfs file systems.
+
cp now preserves time stamps on symbolic links, when possible
cp, install, mv: take advantage of btrfs' O(1) copy-on-write feature
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 90a54b2..bb1d87a 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7543,6 +7543,15 @@ cp invocation
unless you also specify @option{-P}, as @acronym{POSIX} allows
implementations that dereference symbolic links by default.
address@hidden --reflink
address@hidden --reflink
+Perform a lightweight, copy-on-write (COW) copy.
+Copying with this option can succeed only on some relatively new file systems.
+Once it has succeeded, beware that the source and destination files
+share the same disk data blocks as long as they remain unmodified.
+Thus, if a disk I/O error affects data blocks of one of the files,
+the other suffers the exact same fate.
+
@item --remove-destination
@opindex --remove-destination
Remove each existing destination file before attempting to open it
diff --git a/src/copy.c b/src/copy.c
index 24b5f6b..bed90c4 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -624,13 +624,16 @@ copy_reg (char const *src_name, char const *dst_name,
goto close_src_and_dst_desc;
}
- /* If --sparse=auto is in effect, attempt a btrfs clone operation.
- If the operation is not supported or it fails then copy the file
- in the usual way. */
- bool copied = (x->sparse_mode == SPARSE_AUTO
- && clone_file (dest_desc, source_desc) == 0);
+ if (x->reflink)
+ {
+ if (clone_file (dest_desc, source_desc))
+ {
+ error (0, errno, _("failed to clone %s"), quote (dst_name));
+ return_val = false;
+ }
+ goto close_src_and_dst_desc;
+ }
- if (!copied)
{
typedef uintptr_t word;
off_t n_read_total = 0;
@@ -2232,6 +2235,7 @@ valid_options (const struct cp_options *co)
assert (VALID_BACKUP_TYPE (co->backup_type));
assert (VALID_SPARSE_MODE (co->sparse_mode));
assert (!(co->hard_link && co->symbolic_link));
+ assert (!(co->reflink && co->sparse_mode != SPARSE_AUTO));
return true;
}
diff --git a/src/copy.h b/src/copy.h
index 8e0b408..ddf4f4e 100644
--- a/src/copy.h
+++ b/src/copy.h
@@ -219,6 +219,9 @@ struct cp_options
such a symlink) and returns false. */
bool open_dangling_dest_symlink;
+ /* If true, attempt to clone the file instead of copying it. */
+ bool reflink;
+
/* This is a set of destination name/inode/dev triples. Each such triple
represents a file we have created corresponding to a source file name
that was specified on the command line. Use it to avoid clobbering
diff --git a/src/cp.c b/src/cp.c
index 8785076..c99aff3 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -76,6 +76,7 @@ enum
NO_PRESERVE_ATTRIBUTES_OPTION,
PARENTS_OPTION,
PRESERVE_ATTRIBUTES_OPTION,
+ REFLINK_OPTION,
SPARSE_OPTION,
STRIP_TRAILING_SLASHES_OPTION,
UNLINK_DEST_BEFORE_OPENING
@@ -121,6 +122,7 @@ static struct option const long_opts[] =
{"recursive", no_argument, NULL, 'R'},
{"remove-destination", no_argument, NULL, UNLINK_DEST_BEFORE_OPENING},
{"sparse", required_argument, NULL, SPARSE_OPTION},
+ {"reflink", no_argument, NULL, REFLINK_OPTION},
{"strip-trailing-slashes", no_argument, NULL, STRIP_TRAILING_SLASHES_OPTION},
{"suffix", required_argument, NULL, 'S'},
{"symbolic-link", no_argument, NULL, 's'},
@@ -190,6 +192,7 @@ Mandatory arguments to long options are mandatory for short
options too.\n\
"), stdout);
fputs (_("\
-R, -r, --recursive copy directories recursively\n\
+ --reflink perform a lightweight (CoW/clone) copy\n\
--remove-destination remove each existing destination file before\n\
attempting to open it (contrast with
--force)\n\
"), stdout);
@@ -752,6 +755,7 @@ cp_option_init (struct cp_options *x)
x->interactive = I_UNSPECIFIED;
x->move_mode = false;
x->one_file_system = false;
+ x->reflink = false;
x->preserve_ownership = false;
x->preserve_links = false;
@@ -916,6 +920,10 @@ main (int argc, char **argv)
sparse_type_string, sparse_type);
break;
+ case REFLINK_OPTION:
+ x.reflink = true;
+ break;
+
case 'a': /* Like -dR --preserve=all with reduced failure
diagnostics. */
x.dereference = DEREF_NEVER;
x.preserve_links = true;
@@ -1076,6 +1084,12 @@ main (int argc, char **argv)
usage (EXIT_FAILURE);
}
+ if (x.reflink && x.sparse_mode != SPARSE_AUTO)
+ {
+ error (0, 0, _("--reflink can be used only with --sparse=auto"));
+ usage (EXIT_FAILURE);
+ }
+
if (backup_suffix_string)
simple_backup_suffix = xstrdup (backup_suffix_string);
diff --git a/src/install.c b/src/install.c
index fd8f71e..73b3981 100644
--- a/src/install.c
+++ b/src/install.c
@@ -269,6 +269,7 @@ cp_option_init (struct cp_options *x)
{
cp_options_default (x);
x->copy_as_regular = true;
+ x->reflink = false;
x->dereference = DEREF_ALWAYS;
x->unlink_dest_before_opening = true;
x->unlink_dest_after_failed_open = false;
diff --git a/src/mv.c b/src/mv.c
index 8b9b6a1..8d77380 100644
--- a/src/mv.c
+++ b/src/mv.c
@@ -105,6 +105,7 @@ cp_option_init (struct cp_options *x)
cp_options_default (x);
x->copy_as_regular = false; /* FIXME: maybe make this an option */
+ x->reflink = false;
x->dereference = DEREF_NEVER;
x->unlink_dest_before_opening = false;
x->unlink_dest_after_failed_open = false;
diff --git a/tests/cp/sparse b/tests/cp/sparse
index bd1a84f..9683a9e 100755
--- a/tests/cp/sparse
+++ b/tests/cp/sparse
@@ -38,4 +38,8 @@ cp --sparse=always sparse copy || fail=1
# Ensure that the copy has the same block count as the original.
test `stat --printf %b copy` -le `stat --printf %b sparse` || fail=1
+# Ensure that --sparse={always,never} with --reflink fail.
+cp --sparse=always --reflink sparse copy && fail=1
+cp --sparse=never --reflink sparse copy && fail=1
+
Exit $fail
--
1.6.4.161.gc0b1
Re: BTRFS file clone support for cp, Pádraig Brady, 2009/08/10