On 09/14/2015 11:32 PM, Darrick J. Wong wrote:
> On Fri, Sep 11, 2015 at 04:30:21PM -0400, Anna Schumaker wrote:
>> The NFS server will need some kind offallback for filesystems that don't
>> have any kind of copy acceleration, and it should be generally useful to
>> have an in-kernel copy to avoid lots of switches between kernel and user
>> space.
>>
>> I make this configurable by adding two new flags. Users who only want a
>> reflink can pass COPY_FR_REFLINK, and users who want a full data copy can
>> pass COPY_FR_COPY. 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>
>> ---
>> v2:
>> - Rename COPY_REFLINK -> COPY_FR_REFLINK
>> - Introduce COPY_FR_COPY flag
>> - Flags == 0 is really COPY_FR_COPY|COPY_FR_REFLINK
>> - Drop check for invalid flags
>> - Move call to do_splice_direct() into a new function
>> - Move rw_verify_area() checks into the new fallback function
>> ---
>> fs/read_write.c | 56 ++++++++++++++++++++++++++++-------------------
>> include/linux/copy.h | 6 +++++
>> include/uapi/linux/Kbuild | 1 +
>> include/uapi/linux/copy.h | 7 ++++++
>> 4 files changed, 48 insertions(+), 22 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 363bd3e..ba24884 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 +1362,17 @@ 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, int flags)
>> {
>> - struct inode *inode_in;
>> - struct inode *inode_out;
>> ssize_t ret;
>>
>> - if (flags)
>> - 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;
>> + if (flags == 0)
>> + flags = COPY_FR_COPY | COPY_FR_REFLINK;
>
> This function must return -EINVAL if any of the undefined flags bits are
> set.
Sure, I'll add that.
>
>>
>> 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_in->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 +1380,13 @@ 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)
>> + 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 70ff1d9..d46830a 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..2da59a8
>> --- /dev/null
>> +++ b/include/uapi/linux/copy.h
>> @@ -0,0 +1,7 @@
>> +#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. */
>
> Could I have a COPY_FR_DEDUPE flag too, please?
>
> (I don't mind adding it myself when I get around to hooking up XFS, but I
> was hoping to get it in during the first round).
I guess I can, but only iff everybody has agreed on using copy for dedupes instead of somethink like fallocate.
Anna
>
> --D
>
>> +
>> +#endif /* _UAPI_LINUX_COPY_H */
>> --
>> 2.5.1
>>
>> --
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