btrfs: move fiemap code into its own file

Currently the core of the fiemap code lives in extent_io.c, which does
not make any sense because it's not related to extent IO at all (and it
was not as well before the big rewrite of fiemap I did some time ago).
The entry point for fiemap, btrfs_fiemap(), lives in inode.c since it's
an inode operation.

Since there's a significant amount of fiemap code, move all of it into a
dedicated file, including its entry point inode.c:btrfs_fiemap().
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/Makefile

@@ -33,7 +33,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
 	   block-rsv.o delalloc-space.o block-group.o discard.o reflink.o \
 	   subpage.o tree-mod-log.o extent-io-tree.o fs.o messages.o bio.o \
-	   lru_cache.o raid-stripe-tree.o
+	   lru_cache.o raid-stripe-tree.o fiemap.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) += ref-verify.o

fs/btrfs/extent_io.h

@@ -242,8 +242,6 @@ int btrfs_writepages(struct address_space *mapping, struct writeback_control *wb
 int btree_write_cache_pages(struct address_space *mapping,
 			    struct writeback_control *wbc);
 void btrfs_readahead(struct readahead_control *rac);
-int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
-		  u64 start, u64 len);
 int set_folio_extent_mapped(struct folio *folio);
 int set_page_extent_mapped(struct page *page);
 void clear_page_extent_mapped(struct page *page);

fs/btrfs/fiemap.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_FIEMAP_H
+#define BTRFS_FIEMAP_H
+
+#include <linux/fiemap.h>
+
+int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		 u64 start, u64 len);
+
+#endif /* BTRFS_FIEMAP_H */

fs/btrfs/inode.c

@@ -70,6 +70,7 @@
 #include "orphan.h"
 #include "backref.h"
 #include "raid-stripe-tree.h"
+#include "fiemap.h"
 
 struct btrfs_iget_args {
 	u64 ino;
@@ -7929,57 +7930,6 @@ struct iomap_dio *btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter,
 			    IOMAP_DIO_PARTIAL, &data, done_before);
 }
 
-static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
-			u64 start, u64 len)
-{
-	struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
-	int	ret;
-
-	ret = fiemap_prep(inode, fieinfo, start, &len, 0);
-	if (ret)
-		return ret;
-
-	/*
-	 * fiemap_prep() called filemap_write_and_wait() for the whole possible
-	 * file range (0 to LLONG_MAX), but that is not enough if we have
-	 * compression enabled. The first filemap_fdatawrite_range() only kicks
-	 * in the compression of data (in an async thread) and will return
-	 * before the compression is done and writeback is started. A second
-	 * filemap_fdatawrite_range() is needed to wait for the compression to
-	 * complete and writeback to start. We also need to wait for ordered
-	 * extents to complete, because our fiemap implementation uses mainly
-	 * file extent items to list the extents, searching for extent maps
-	 * only for file ranges with holes or prealloc extents to figure out
-	 * if we have delalloc in those ranges.
-	 */
-	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
-		ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
-		if (ret)
-			return ret;
-	}
-
-	btrfs_inode_lock(btrfs_inode, BTRFS_ILOCK_SHARED);
-
-	/*
-	 * We did an initial flush to avoid holding the inode's lock while
-	 * triggering writeback and waiting for the completion of IO and ordered
-	 * extents. Now after we locked the inode we do it again, because it's
-	 * possible a new write may have happened in between those two steps.
-	 */
-	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) {
-		ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX);
-		if (ret) {
-			btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
-			return ret;
-		}
-	}
-
-	ret = extent_fiemap(btrfs_inode, fieinfo, start, len);
-	btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED);
-
-	return ret;
-}
-
 /*
  * For release_folio() and invalidate_folio() we have a race window where
  * folio_end_writeback() is called but the subpage spinlock is not yet released.