On 09/28/2015 02:31 PM, Darrick J. Wong wrote:
> On Fri, Sep 25, 2015 at 04:48:14PM -0400, Anna Schumaker wrote:
>> The NFS server will need some kind offallback for filesystems that don't
>
> "some kind of fallback"
I'll rephrase that :)
>
>> 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.
>
> "The COPY_FR_DEDUPE flag makes a reflink, but only if the contents of both
> file ranges are identical."
Sure. I'll point that out in the man page.
>
>> 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>
>> ---
>> v3:
>> - Check that both filesystems have the same filesystem type
>> - Add COPY_FR_DEDUPE flag for Darrick
>> - Check that at most one flag is set at a time
>> ---
>> 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..a0fd9dc 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_DEDUPE)
>> + return -EOPNOTSUPP;
>
> Since dedupe can't be combined with copy or reflink either, we might as well
> say:
>
> if ((flags & COPY_FR_DEDUPE) && (flags & ~COPY_FR_DEDUPE))
> return -EINVAL;
>
> and let the per-fs copy_file_range()s dispatch appropriately.
That makes sense. I was thinking that could be changed when dedupe is added, but I guess that defeats the purpose of adding the flag during the initial merge.
Anna
>
> Otherwise, you can add:
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> --D
>
>>
>> - /* 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..6225838
>> --- /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_DEDUPE (1 << 2) /* Deduplicate file data. */
>> +
>> +#endif /* _UAPI_LINUX_COPY_H */
>> --
>> 2.5.3
>>
>> --
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