[PATCH] ext4: Implement swap_activate aops using iomap

[Ritesh Harjani]

After moving ext4's bmap to iomap interface, swapon functionality
on files created using fallocate (which creates unwritten extents) are
failing. This is since iomap_bmap interface returns 0 for unwritten
extents and thus generic_swapfile_activate considers this as holes
and hence bail out with below kernel msg :-

[340.915835] swapon: swapfile has holes

To fix this we need to implement ->swap_activate aops in ext4
which will use ext4_iomap_report_ops. Since we only need to return
the list of extents so ext4_iomap_report_ops should be enough.

Reported-by: Yuxuan Shui <yshu...@gmail.com>
Fixes: ac58e4fb03f ("ext4: move ext4 bmap to use iomap infrastructure")
Signed-off-by: Ritesh Harjani <rite...@linux.ibm.com>
---
[Tested xfstests with -g swap; Tested stress-ng with --thrash option]

 fs/ext4/inode.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1556cabd3a7d..9ac0f83e6fbe 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3605,6 +3605,13 @@ static int ext4_set_page_dirty(struct page *page)
        return __set_page_dirty_buffers(page);
 }
 
+static int ext4_iomap_swap_activate(struct swap_info_struct *sis,
+                                   struct file *file, sector_t *span)
+{
+       return iomap_swapfile_activate(sis, file, span,
+                                      &ext4_iomap_report_ops);
+}
+
 static const struct address_space_operations ext4_aops = {
        .readpage               = ext4_readpage,
        .readpages              = ext4_readpages,
@@ -3620,6 +3627,7 @@ static const struct address_space_operations ext4_aops = {
        .migratepage            = buffer_migrate_page,
        .is_partially_uptodate  = block_is_partially_uptodate,
        .error_remove_page      = generic_error_remove_page,
+       .swap_activate          = ext4_iomap_swap_activate,
 };
 
 static const struct address_space_operations ext4_journalled_aops = {
@@ -3636,6 +3644,7 @@ static const struct address_space_operations 
ext4_journalled_aops = {
        .direct_IO              = noop_direct_IO,
        .is_partially_uptodate  = block_is_partially_uptodate,
        .error_remove_page      = generic_error_remove_page,
+       .swap_activate          = ext4_iomap_swap_activate,
 };
 
 static const struct address_space_operations ext4_da_aops = {
@@ -3653,6 +3662,7 @@ static const struct address_space_operations ext4_da_aops 
= {
        .migratepage            = buffer_migrate_page,
        .is_partially_uptodate  = block_is_partially_uptodate,
        .error_remove_page      = generic_error_remove_page,
+       .swap_activate          = ext4_iomap_swap_activate,
 };
 
 static const struct address_space_operations ext4_dax_aops = {
@@ -3661,6 +3671,7 @@ static const struct address_space_operations 
ext4_dax_aops = {
        .set_page_dirty         = noop_set_page_dirty,
        .bmap                   = ext4_bmap,
        .invalidatepage         = noop_invalidatepage,
+       .swap_activate          = ext4_iomap_swap_activate,
 };
 
 void ext4_set_aops(struct inode *inode)
-- 
2.25.1