[PATCH] erofs: use GFP_NOIO in endio decompression path of erofs

[Jiucheng Xu via B4 Relay]

From: Jiucheng Xu <jiucheng.xu at amlogic.com>

The endio decompression path of erofs calls vm_map_ram(). Due to
insufficient memory, this function may generate memory swapping I/O,
which can cause submit_bio_wait to deadlock in some scenarios.

Trimmed down the call stack, as follows:

f2fs_submit_read_io
  submit_bio                      //bio_list is initialized.
    mmc_blk_mq_recovery
      z_erofs_endio
        vm_map_ram
          __pte_alloc_kernel
            __alloc_pages_direct_reclaim
              shrink_folio_list
                __swap_writepage
                  submit_bio_wait  //bio_list is non-NULL, hang!!!

Use memalloc_noio_{save,restore}() to wrap up this path.

Signed-off-by: Jiucheng Xu <jiucheng.xu at amlogic.com>
---
 fs/erofs/zdata.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 3977e42b9516861bf3d59c072b6b8aaa6898dd8a..fe8121df9ef2f2404fc6e3f0fbbd6367f9ec2c67 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1445,6 +1445,7 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 				       int bios)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
+	int gfp_flag;
 
 	/* wake up the caller thread for sync decompression */
 	if (io->sync) {
@@ -1477,7 +1478,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 			sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
 		return;
 	}
+	gfp_flag = memalloc_noio_save();
 	z_erofs_decompressqueue_work(&io->u.work);
+	memalloc_noio_restore(gfp_flag);
 }
 
 static void z_erofs_fill_bio_vec(struct bio_vec *bvec,

---
base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
change-id: 20260311-origin-dev-1c9665798204

Best regards,
-- 
Jiucheng Xu <jiucheng.xu at amlogic.com>