This allows us to have an in-kernel copy mechanism that avoids frequent
switches between kernel and user space. This is especially useful so
NFSD can support server-side copies.
I make pagecache copies configurable by adding three new (exclusive)
flags:
- COPY_FR_REFLINK tells vfs_copy_file_range() to only create a reflink.
- COPY_FR_COPY does a full data copy, but may be filesystem accelerated.
- COPY_FR_DEDUP creates a reflink, but only if the contents of both
ranges are identical.
The default (flags=0) means to first attempt a reflink, but use the pagecache
if that fails.
I moved the rw_verify_area() calls into the fallback code since some
filesystems can handle reflinking a large range.
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
v4:
- Reword commit message
- Rename COPY_FR_DEDUPE -> COPY_FR_DEDUP
---
fs/read_write.c | 61 +++++++++++++++++++++++++++++++----------------
include/linux/copy.h | 6 +++++
include/uapi/linux/Kbuild | 1 +
include/uapi/linux/copy.h | 8 +++++++
4 files changed, 56 insertions(+), 20 deletions(-)
create mode 100644 include/linux/copy.h
create mode 100644 include/uapi/linux/copy.h
diff --git a/fs/read_write.c b/fs/read_write.c
index ee9fa37..4fb9b8e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -7,6 +7,7 @@
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
+#include <linux/copy.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/fsnotify.h>
@@ -1329,6 +1330,29 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
}
#endif
+static ssize_t vfs_copy_file_pagecache(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ size_t len)
+{
+ ssize_t ret;
+
+ ret = rw_verify_area(READ, file_in, &pos_in, len);
+ if (ret >= 0) {
+ len = ret;
+ ret = rw_verify_area(WRITE, file_out, &pos_out, len);
+ if (ret >= 0)
+ len = ret;
+ }
+ if (ret < 0)
+ return ret;
+
+ file_start_write(file_out);
+ ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out, len, 0);
+ file_end_write(file_out);
+
+ 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
@@ -1338,34 +1362,26 @@ ssize_t vfs_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)
{
- struct inode *inode_in;
- struct inode *inode_out;
ssize_t ret;
- if (flags)
+ /* Flags should only be used exclusively. */
+ if ((flags & COPY_FR_COPY) && (flags & ~COPY_FR_COPY))
+ return -EINVAL;
+ if ((flags & COPY_FR_REFLINK) && (flags & ~COPY_FR_REFLINK))
+ return -EINVAL;
+ if ((flags & COPY_FR_DEDUP) && (flags & ~COPY_FR_DEDUP))
return -EINVAL;
- /* copy_file_range allows full ssize_t len, ignoring MAX_RW_COUNT */
- ret = rw_verify_area(READ, file_in, &pos_in, len);
- if (ret >= 0)
- ret = rw_verify_area(WRITE, file_out, &pos_out, len);
- if (ret < 0)
- return ret;
+ /* Default behavior is to try both. */
+ if (flags == 0)
+ flags = COPY_FR_COPY | COPY_FR_REFLINK;
if (!(file_in->f_mode & FMODE_READ) ||
!(file_out->f_mode & FMODE_WRITE) ||
(file_out->f_flags & O_APPEND) ||
- !file_out->f_op || !file_out->f_op->copy_file_range)
+ !file_out->f_op)
return -EBADF;
- inode_in = file_inode(file_in);
- inode_out = file_inode(file_out);
-
- /* make sure offsets don't wrap and the input is inside i_size */
- if (pos_in + len < pos_in || pos_out + len < pos_out ||
- pos_in + len > i_size_read(inode_in))
- return -EINVAL;
-
if (len == 0)
return 0;
@@ -1373,8 +1389,13 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
if (ret)
return ret;
- ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out, pos_out,
- len, flags);
+ ret = -EOPNOTSUPP;
+ if (file_out->f_op->copy_file_range && (file_in->f_op == file_out->f_op))
+ ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out,
+ pos_out, len, flags);
+ if ((ret < 0) && (flags & COPY_FR_COPY))
+ ret = vfs_copy_file_pagecache(file_in, pos_in, file_out,
+ pos_out, len);
if (ret > 0) {
fsnotify_access(file_in);
add_rchar(current, ret);
diff --git a/include/linux/copy.h b/include/linux/copy.h
new file mode 100644
index 0000000..fd54543
--- /dev/null
+++ b/include/linux/copy.h
@@ -0,0 +1,6 @@
+#ifndef _LINUX_COPY_H
+#define _LINUX_COPY_H
+
+#include <uapi/linux/copy.h>
+
+#endif /* _LINUX_COPY_H */
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index f7b2db4..faafd67 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -90,6 +90,7 @@ header-y += coda_psdev.h
header-y += coff.h
header-y += connector.h
header-y += const.h
+header-y += copy.h
header-y += cramfs_fs.h
header-y += cuda.h
header-y += cyclades.h
diff --git a/include/uapi/linux/copy.h b/include/uapi/linux/copy.h
new file mode 100644
index 0000000..b807dcd
--- /dev/null
+++ b/include/uapi/linux/copy.h
@@ -0,0 +1,8 @@
+#ifndef _UAPI_LINUX_COPY_H
+#define _UAPI_LINUX_COPY_H
+
+#define COPY_FR_COPY (1 << 0) /* Only do a pagecache copy. */
+#define COPY_FR_REFLINK (1 << 1) /* Only make a reflink. */
+#define COPY_FR_DEDUP (1 << 2) /* Deduplicate file data. */
+
+#endif /* _UAPI_LINUX_COPY_H */
--
2.5.3
--
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