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Subject[PATCH] dax: try to avoid unused function warnings
Without the get_block based I/O, we get warnings when CONFIG_FS_IOMAP
is disabled:

fs/dax.c:736:12: error: ‘dax_insert_mapping’ defined but not used [-Werror=unused-function]
fs/dax.c:512:12: error: ‘copy_user_dax’ defined but not used [-Werror=unused-function]
fs/dax.c:490:12: error: ‘dax_load_hole’ defined but not used [-Werror=unused-function]
fs/dax.c:294:14: error: ‘grab_mapping_entry’ defined but not used [-Werror=unused-function]

This patch blindly marks those as __maybe_unused, which avoids the warnings.
However, I suspect that there is actually more code in this file that should
not be provided without CONFIG_FS_IOMAP even though we don't get a warning
for it, and that we actually want a different rework, so please treat this
as a bug report. I have applied the patch locally in my randconfig build
setup to avoid seeing the warnings.

Fixes: 5ac65736f740 ("dax: rip out get_block based IO support")
Signed-off-by: Arnd Bergmann <>
fs/dax.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index b1fe228cd609..cf844e77b7b7 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -309,7 +309,7 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
* persistent memory the benefit is doubtful. We can add that later if we can
* show it helps.
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+static __maybe_unused void * grab_mapping_entry(struct address_space *mapping, pgoff_t index,
unsigned long size_flag)
bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
@@ -489,7 +489,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
* otherwise it will simply fall out of the page cache under memory
* pressure without ever having been dirtied.
-static int dax_load_hole(struct address_space *mapping, void *entry,
+static int __maybe_unused dax_load_hole(struct address_space *mapping, void *entry,
struct vm_fault *vmf)
struct page *page;
@@ -509,7 +509,7 @@ static int dax_load_hole(struct address_space *mapping, void *entry,

-static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
+static int __maybe_unused copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
struct page *to, unsigned long vaddr)
struct blk_dax_ctl dax = {
@@ -815,7 +815,7 @@ int dax_writeback_mapping_range(struct address_space *mapping,

-static int dax_insert_mapping(struct address_space *mapping,
+static int __maybe_unused dax_insert_mapping(struct address_space *mapping,
struct block_device *bdev, sector_t sector, size_t size,
void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
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