ext4: Switch to iomap for SEEK_HOLE / SEEK_DATA

Switch to the iomap_seek_hole and iomap_seek_data helpers for
implementing lseek SEEK_HOLE / SEEK_DATA, and remove all the code that
isn't needed any more.

Note that with this patch ext4 will now always depend on the iomap code
instead of only when CONFIG_DAX is enabled, and it requires adding a
call into the extent status tree for iomap_begin as well to properly
deal with delalloc extents.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
[More fixes and cleanups by Andreas]

1 files changed, 34 insertions, 75 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7755f41bdfc3..edfe95f81274 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3393,7 +3393,6 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
 		return try_to_free_buffers(page);
 }
 
-#ifdef CONFIG_FS_DAX
 static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 			    unsigned flags, struct iomap *iomap)
 {
@@ -3402,6 +3401,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	unsigned long first_block = offset >> blkbits;
 	unsigned long last_block = (offset + length - 1) >> blkbits;
 	struct ext4_map_blocks map;
+	bool delalloc = false;
 	int ret;
 
 
@@ -3422,9 +3422,33 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	map.m_lblk = first_block;
 	map.m_len = last_block - first_block + 1;
 
-	if (!(flags & IOMAP_WRITE)) {
+	if (flags & IOMAP_REPORT) {
 		ret = ext4_map_blocks(NULL, inode, &map, 0);
-	} else {
+		if (ret < 0)
+			return ret;
+
+		if (ret == 0) {
+			ext4_lblk_t end = map.m_lblk + map.m_len - 1;
+			struct extent_status es;
+
+			ext4_es_find_delayed_extent_range(inode, map.m_lblk, end, &es);
+
+			if (!es.es_len || es.es_lblk > end) {
+				/* entire range is a hole */
+			} else if (es.es_lblk > map.m_lblk) {
+				/* range starts with a hole */
+				map.m_len = es.es_lblk - map.m_lblk;
+			} else {
+				ext4_lblk_t offs = 0;
+
+				if (es.es_lblk < map.m_lblk)
+					offs = map.m_lblk - es.es_lblk;
+				map.m_lblk = es.es_lblk + offs;
+				map.m_len = es.es_len - offs;
+				delalloc = true;
+			}
+		}
+	} else if (flags & IOMAP_WRITE) {
 		int dio_credits;
 		handle_t *handle;
 		int retries = 0;
@@ -3475,17 +3499,21 @@ retry:
 			}
 		}
 		ext4_journal_stop(handle);
+	} else {
+		ret = ext4_map_blocks(NULL, inode, &map, 0);
+		if (ret < 0)
+			return ret;
 	}
 
 	iomap->flags = 0;
 	iomap->bdev = inode->i_sb->s_bdev;
 	iomap->dax_dev = sbi->s_daxdev;
 	iomap->offset = first_block << blkbits;
+	iomap->length = (u64)map.m_len << blkbits;
 
 	if (ret == 0) {
-		iomap->type = IOMAP_HOLE;
+		iomap->type = delalloc ? IOMAP_DELALLOC : IOMAP_HOLE;
 		iomap->addr = IOMAP_NULL_ADDR;
-		iomap->length = (u64)map.m_len << blkbits;
 	} else {
 		if (map.m_flags & EXT4_MAP_MAPPED) {
 			iomap->type = IOMAP_MAPPED;
@@ -3496,11 +3524,11 @@ retry:
 			return -EIO;
 		}
 		iomap->addr = (u64)map.m_pblk << blkbits;
-		iomap->length = (u64)map.m_len << blkbits;
 	}
 
 	if (map.m_flags & EXT4_MAP_NEW)
 		iomap->flags |= IOMAP_F_NEW;
+
 	return 0;
 }
 
@@ -3561,8 +3589,6 @@ const struct iomap_ops ext4_iomap_ops = {
 	.iomap_end		= ext4_iomap_end,
 };
 
-#endif
-
 static int ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
 			    ssize_t size, void *private)
 {
@@ -6118,70 +6144,3 @@ int ext4_filemap_fault(struct vm_fault *vmf)
 
 	return err;
 }
-
-/*
- * Find the first extent at or after @lblk in an inode that is not a hole.
- * Search for @map_len blocks at most. The extent is returned in @result.
- *
- * The function returns 1 if we found an extent. The function returns 0 in
- * case there is no extent at or after @lblk and in that case also sets
- * @result->es_len to 0. In case of error, the error code is returned.
- */
-int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
-			 unsigned int map_len, struct extent_status *result)
-{
-	struct ext4_map_blocks map;
-	struct extent_status es = {};
-	int ret;
-
-	map.m_lblk = lblk;
-	map.m_len = map_len;
-
-	/*
-	 * For non-extent based files this loop may iterate several times since
-	 * we do not determine full hole size.
-	 */
-	while (map.m_len > 0) {
-		ret = ext4_map_blocks(NULL, inode, &map, 0);
-		if (ret < 0)
-			return ret;
-		/* There's extent covering m_lblk? Just return it. */
-		if (ret > 0) {
-			int status;
-
-			ext4_es_store_pblock(result, map.m_pblk);
-			result->es_lblk = map.m_lblk;
-			result->es_len = map.m_len;
-			if (map.m_flags & EXT4_MAP_UNWRITTEN)
-				status = EXTENT_STATUS_UNWRITTEN;
-			else
-				status = EXTENT_STATUS_WRITTEN;
-			ext4_es_store_status(result, status);
-			return 1;
-		}
-		ext4_es_find_delayed_extent_range(inode, map.m_lblk,
-						  map.m_lblk + map.m_len - 1,
-						  &es);
-		/* Is delalloc data before next block in extent tree? */
-		if (es.es_len && es.es_lblk < map.m_lblk + map.m_len) {
-			ext4_lblk_t offset = 0;
-
-			if (es.es_lblk < lblk)
-				offset = lblk - es.es_lblk;
-			result->es_lblk = es.es_lblk + offset;
-			ext4_es_store_pblock(result,
-					     ext4_es_pblock(&es) + offset);
-			result->es_len = es.es_len - offset;
-			ext4_es_store_status(result, ext4_es_status(&es));
-
-			return 1;
-		}
-		/* There's a hole at m_lblk, advance us after it */
-		map.m_lblk += map.m_len;
-		map_len -= map.m_len;
-		map.m_len = map_len;
-		cond_resched();
-	}
-	result->es_len = 0;
-	return 0;
-}