From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Plumb in a remap flag that enables the filesystem remap handler to
shorten remapping requests for callers that can handle it. Now
copy_file_range can report partial success (in case we run up against
alignment problems, resource limits, etc.).
We also enable CAN_SHORTEN for fideduperange to maintain existing
userspace-visible behavior where xfs/btrfs shorten the dedupe range to
avoid stale post-eof data exposure.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/read_write.c | 28 ++++++++++++++++++++--------
include/linux/fs.h | 7 +++++--
mm/filemap.c | 16 ++++++++++++----
3 files changed, 37 insertions(+), 14 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index f6ab5beb935a..ee9314b7bfc3 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1593,7 +1593,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
cloned = file_in->f_op->remap_file_range(file_in, pos_in,
file_out, pos_out,
- min_t(loff_t, MAX_RW_COUNT, len), 0);
+ min_t(loff_t, MAX_RW_COUNT, len),
+ REMAP_FILE_CAN_SHORTEN);
if (cloned > 0) {
ret = cloned;
goto done;
@@ -1721,6 +1722,8 @@ static int remap_verify_area(struct file *file, loff_t pos, loff_t len,
* can't meaningfully compare post-EOF contents.
*
* For clone we only link a partial EOF block above the destination file's EOF.
+ *
+ * Shorten the request if possible.
*/
static int generic_remap_check_len(struct inode *inode_in,
struct inode *inode_out,
@@ -1729,16 +1732,24 @@ static int generic_remap_check_len(struct inode *inode_in,
unsigned int remap_flags)
{
u64 blkmask = i_blocksize(inode_in) - 1;
+ loff_t new_len = *len;
if ((*len & blkmask) == 0)
return 0;
- if (remap_flags & REMAP_FILE_DEDUP)
- *len &= ~blkmask;
- else if (pos_out + *len < i_size_read(inode_out))
- return -EINVAL;
+ if ((remap_flags & REMAP_FILE_DEDUP) ||
+ pos_out + *len < i_size_read(inode_out))
+ new_len &= ~blkmask;
- return 0;
+ if (new_len == *len)
+ return 0;
+
+ if (remap_flags & REMAP_FILE_CAN_SHORTEN) {
+ *len = new_len;
+ return 0;
+ }
+
+ return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL;
}
/* Update inode timestamps and remove security privileges when remapping. */
@@ -2023,7 +2034,8 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
{
loff_t ret;
- WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP));
+ WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP |
+ REMAP_FILE_CAN_SHORTEN));
ret = mnt_want_write_file(dst_file);
if (ret)
@@ -2124,7 +2136,7 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
deduped = vfs_dedupe_file_range_one(file, off, dst_file,
info->dest_offset, len,
- 0);
+ REMAP_FILE_CAN_SHORTEN);
if (deduped == -EBADE)
info->status = FILE_DEDUPE_RANGE_DIFFERS;
else if (deduped < 0)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c0ae85a7bd9d..594fe4ba0b15 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1726,14 +1726,17 @@ struct block_device_operations;
* If it is called with len == 0 that means "remap to end of source file".
*
* REMAP_FILE_DEDUP: only remap if contents identical (i.e. deduplicate)
+ * REMAP_FILE_CAN_SHORTEN: caller can handle a shortened request
*/
#define REMAP_FILE_DEDUP (1 << 0)
+#define REMAP_FILE_CAN_SHORTEN (1 << 1)
/* All valid REMAP_FILE flags */
-#define REMAP_FILE_VALID_FLAGS (REMAP_FILE_DEDUP)
+#define REMAP_FILE_VALID_FLAGS (REMAP_FILE_DEDUP | \
+ REMAP_FILE_CAN_SHORTEN)
/* REMAP_FILE flags taken care of by the vfs. */
-#define REMAP_FILE_ADVISORY (0)
+#define REMAP_FILE_ADVISORY (REMAP_FILE_CAN_SHORTEN)
struct iov_iter;
diff --git a/mm/filemap.c b/mm/filemap.c
index 1e93269efafe..898eb358f7d2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3051,8 +3051,12 @@ int generic_remap_checks(struct file *file_in, loff_t pos_in,
if (pos_in + count == size_in) {
bcount = ALIGN(size_in, bs) - pos_in;
} else {
- if (!IS_ALIGNED(count, bs))
- return -EINVAL;
+ if (!IS_ALIGNED(count, bs)) {
+ if (remap_flags & REMAP_FILE_CAN_SHORTEN)
+ count = ALIGN_DOWN(count, bs);
+ else
+ return -EINVAL;
+ }
bcount = count;
}
@@ -3063,10 +3067,14 @@ int generic_remap_checks(struct file *file_in, loff_t pos_in,
pos_out < pos_in + bcount)
return -EINVAL;
- /* For now we don't support changing the length. */
- if (*req_count != count)
+ /*
+ * We shortened the request but the caller can't deal with that, so
+ * bounce the request back to userspace.
+ */
+ if (*req_count != count && !(remap_flags & REMAP_FILE_CAN_SHORTEN))
return -EINVAL;
+ *req_count = count;
return 0;
}
