@@ -1144,3 +1144,48 @@ xfs_xattr_iomap_begin(
struct iomap_ops xfs_xattr_iomap_ops = {
.iomap_begin = xfs_xattr_iomap_begin,
};
+
+static int
+xfs_cow_iomap_begin(
+ struct inode *inode,
+ loff_t offset,
+ loff_t length,
+ unsigned flags,
+ struct iomap *iomap)
+{
+ struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
+ xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, offset + length);
+ struct xfs_bmbt_irec imap;
+ int error = 0;
+ int nimaps = 1;
+ unsigned lockmode;
+
+ if (XFS_FORCED_SHUTDOWN(mp))
+ return -EIO;
+
+ lockmode = xfs_ilock_data_map_shared(ip);
+
+ if (!xfs_is_reflink_inode(ip)) {
+ error = -ENOENT;
+ goto out_unlock;
+ }
+
+ error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+ &nimaps, XFS_BMAPI_ENTIRE | XFS_BMAPI_COWFORK);
+
+out_unlock:
+ xfs_iunlock(ip, lockmode);
+
+ if (!error) {
+ ASSERT(nimaps);
+ xfs_bmbt_to_iomap(ip, iomap, &imap);
+ }
+
+ return error;
+}
+
+struct iomap_ops xfs_cow_iomap_ops = {
+ .iomap_begin = xfs_cow_iomap_begin,
+};
@@ -35,5 +35,6 @@ xfs_extlen_t xfs_eof_alignment(struct xfs_inode *ip, xfs_extlen_t extsize);
extern struct iomap_ops xfs_iomap_ops;
extern struct iomap_ops xfs_xattr_iomap_ops;
+extern struct iomap_ops xfs_cow_iomap_ops;
#endif /* __XFS_IOMAP_H__*/
@@ -1043,6 +1043,10 @@ xfs_vn_fiemap(
fieinfo->fi_flags &= ~FIEMAP_FLAG_XATTR;
error = iomap_fiemap(inode, fieinfo, start, length,
&xfs_xattr_iomap_ops);
+ } else if (fieinfo->fi_flags & FIEMAP_FLAG_COW) {
+ fieinfo->fi_flags &= ~FIEMAP_FLAG_COW;
+ error = iomap_fiemap(inode, fieinfo, start, length,
+ &xfs_cow_iomap_ops);
} else {
error = iomap_fiemap(inode, fieinfo, start, length,
&xfs_iomap_ops);
@@ -41,6 +41,7 @@ struct fiemap {
#define FIEMAP_FLAG_SYNC 0x00000001 /* sync file data before map */
#define FIEMAP_FLAG_XATTR 0x00000002 /* map extended attribute tree */
#define FIEMAP_FLAG_CACHE 0x00000004 /* request caching of the extents */
+#define FIEMAP_FLAG_COW 0x00000010 /* map cow fork extents */
#define FIEMAP_FLAGS_COMPAT (FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR)
Reflink support for XFS incorporates the addition of a copy-on-write inode fork to track newly allocated extents to be used to replace shared blocks on write. While these extents are tracked by the cow fork temporarily in principle, fragmentation avoidance mechanisms like the cowextsize hint allow for the allocation of additional blocks outside of the range of the write, in anticipation of future writes. In summary, this means that blocks in the cow fork can linger for some time until written to and remapped to the data fork or reaped by the background cow fork reclaimer. Define and wiree up a fiemap flag to query the cow fork extent list of an inode. Note that fiemap triggers writeback, which means all cow fork extents that are the target of I/O are remapped to the data fork as part of the query. As a result, the cow fork fiemap request returns only the blocks that have been allocated and not yet written to or reclaimed. Signed-off-by: Brian Foster <bfoster@redhat.com> --- fs/xfs/xfs_iomap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ fs/xfs/xfs_iomap.h | 1 + fs/xfs/xfs_iops.c | 4 ++++ include/uapi/linux/fiemap.h | 1 + 4 files changed, 51 insertions(+)