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vfs: allow copy_file_range to copy across devices

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We want to enable cross-filesystem copy_file_range functionality
where possible, so push the "same superblock only" checks down to
the individual filesystem callouts so they can make their own
decisions about cross-superblock copy offload and fallack to
generic_copy_file_range() for cross-superblock copy.

[Amir] We do not call ->remap_file_range() in case the files are not
on the same sb and do not call ->copy_file_range() in case the files
do not belong to the same filesystem driver.

This changes behavior of the copy_file_range(2) syscall, which will
now allow cross filesystem in-kernel copy.  CIFS already supports
cross-superblock copy, between two shares to the same server. This
functionality will now be available via the copy_file_range(2) syscall.

Cc: Steve French <stfrench@microsoft.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Amir Goldstein
2019-06-05 08:04:50 -07:00
committed by Darrick J. Wong
parent 8c3f406c09
commit 5dae222a5f
5 changed files with 24 additions and 10 deletions
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18
fs/read_write.c
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@@ -1599,7 +1599,16 @@ static ssize_t do_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)
{
if (file_out->f_op->copy_file_range)
/*
* Although we now allow filesystems to handle cross sb copy, passing
* a file of the wrong filesystem type to filesystem driver can result
* in an attempt to dereference the wrong type of ->private_data, so
* avoid doing that until we really have a good reason. NFS defines
* several different file_system_type structures, but they all end up
* using the same ->copy_file_range() function pointer.
*/
if (file_out->f_op->copy_file_range &&
file_out->f_op->copy_file_range == file_in->f_op->copy_file_range)
return file_out->f_op->copy_file_range(file_in, pos_in,
file_out, pos_out,
len, flags);
@@ -1622,10 +1631,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
if (flags != 0)
return -EINVAL;
/* this could be relaxed once a method supports cross-fs copies */
if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
return -EXDEV;
ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
flags);
if (unlikely(ret))
@@ -1648,7 +1653,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
* Try cloning first, this is supported by more file systems, and
* more efficient if both clone and copy are supported (e.g. NFS).
*/
if (file_in->f_op->remap_file_range) {
if (file_in->f_op->remap_file_range &&
file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {
loff_t cloned;
cloned = file_in->f_op->remap_file_range(file_in, pos_in,