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vfs: Add vfs_copy_file_range() support for pagecache copies 

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.

The default (flags=0) means to first attempt copy acceleration, but use
the pagecache if that fails.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Padraig Brady <P@draigBrady.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Anna Schumaker 2015-11-10 16:53:33 -05:00 committed by Al Viro
parent 3db11b2eec
commit eac70053a1
1 changed files with 9 additions and 4 deletions
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13
fs/read_write.c
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@ -1354,8 +1354,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
if (!(file_in->f_mode & FMODE_READ) ||
!(file_out->f_mode & FMODE_WRITE) ||
(file_out->f_flags & O_APPEND) ||
!file_out->f_op->copy_file_range)
(file_out->f_flags & O_APPEND))
return -EBADF;
/* this could be relaxed once a method supports cross-fs copies */
@ -1369,8 +1368,14 @@ 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 == -EOPNOTSUPP)
ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
if (ret > 0) {
fsnotify_access(file_in);
add_rchar(current, ret);