[PATCH 24/25] xfs: support returning partial reflink results

Darrick J. Wong
2018-10-13T00:08:32Z

Back when the XFS reflink code only supported clone_file_range, we were
only able to return zero or negative error codes to userspace. However,
now that copy_file_range (which returns bytes copied) can use XFS'
clone_file_range, we have the opportunity to return partial results.
For example, if userspace sends a 1GB clone request and we run out of
space halfway through, we at least can tell userspace that we completed
512M of that request like a regular write.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_file.c | 5 +----
fs/xfs/xfs_reflink.c | 20 +++++++++++++++-----
fs/xfs/xfs_reflink.h | 2 +-
3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index bc9e94bcb7a3..b2b15b8dc4a1 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -928,14 +928,11 @@ xfs_file_remap_range(
loff_t len,
unsigned int remap_flags)
{
- int ret;
-
if (!remap_check_flags(remap_flags, RFR_SAME_DATA))
return -EINVAL;

- ret = xfs_reflink_remap_range(file_in, pos_in, file_out, pos_out,
+ return xfs_reflink_remap_range(file_in, pos_in, file_out, pos_out,
len, remap_flags);
- return ret < 0 ? ret : len;
}

STATIC int
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index e1592e751cc2..66a8ddb9c058 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1123,6 +1123,7 @@ xfs_reflink_remap_blocks(
struct xfs_inode *dest,
xfs_fileoff_t destoff,
xfs_filblks_t len,
+ xfs_filblks_t *remapped_len,
xfs_off_t new_isize)
{
struct xfs_bmbt_irec imap;
@@ -1130,6 +1131,7 @@ xfs_reflink_remap_blocks(
int error = 0;
xfs_filblks_t range_len;

+ *remapped_len = 0;
/* drange = (destoff, destoff + len); srange = (srcoff, srcoff + len) */
while (len) {
uint lock_mode;
@@ -1168,6 +1170,7 @@ xfs_reflink_remap_blocks(
srcoff += range_len;
destoff += range_len;
len -= range_len;
+ *remapped_len += range_len;
}

return 0;
@@ -1391,7 +1394,7 @@ xfs_reflink_remap_prep(
/*
* Link a range of blocks from one file to another.
*/
-int
+loff_t
xfs_reflink_remap_range(
struct file *file_in,
loff_t pos_in,
@@ -1406,9 +1409,10 @@ xfs_reflink_remap_range(
struct xfs_inode *dest = XFS_I(inode_out);
struct xfs_mount *mp = src->i_mount;
xfs_fileoff_t sfsbno, dfsbno;
- xfs_filblks_t fsblen;
+ xfs_filblks_t fsblen, remappedfsb = 0;
+ loff_t remapped_bytes = 0;
xfs_extlen_t cowextsize;
- ssize_t ret;
+ int ret;

if (!xfs_sb_version_hasreflink(&mp->m_sb))
return -EOPNOTSUPP;
@@ -1424,11 +1428,17 @@ xfs_reflink_remap_range(

trace_xfs_reflink_remap_range(src, pos_in, len, dest, pos_out);

+ if (len == 0) {
+ ret = 0;
+ goto out_unlock;
+ }
+
dfsbno = XFS_B_TO_FSBT(mp, pos_out);
sfsbno = XFS_B_TO_FSBT(mp, pos_in);
fsblen = XFS_B_TO_FSB(mp, len);
ret = xfs_reflink_remap_blocks(src, sfsbno, dest, dfsbno, fsblen,
- pos_out + len);
+ &remappedfsb, pos_out + len);
+ remapped_bytes = min_t(int64_t, len, XFS_FSB_TO_B(mp, remappedfsb));
if (ret)
goto out_unlock;

@@ -1451,7 +1461,7 @@ xfs_reflink_remap_range(
xfs_reflink_remap_unlock(file_in, file_out);
if (ret)
trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
- return ret;
+ return remapped_bytes > 0 ? remapped_bytes : ret;
}

/*
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index c3c46c276fe1..cbc26ff79a8f 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -27,7 +27,7 @@ extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset,
extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,
xfs_off_t count);
extern int xfs_reflink_recover_cow(struct xfs_mount *mp);
-extern int xfs_reflink_remap_range(struct file *file_in, loff_t pos_in,
+extern loff_t xfs_reflink_remap_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, loff_t len,
unsigned int remap_flags);
extern int xfs_reflink_inode_has_shared_extents(struct xfs_trans *tp,