[f2fs-dev] [PATCH v2 1/2] f2fs: quota: do not use GFP_NOFS in f2fs_quota_read()

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

Commit 02117b8ae9c0 ("f2fs: Set GF_NOFS in read_cache_page_gfp while doing
f2fs_quota_read") adds GFP_NOFS in f2fs_quota_read() to avoid below deadlock:

- do_sys_open
 - vfs_open
  - dquot_file_open
   - dquot_initialize
    - dqget
     - dquot_acquire
      : locks &dqopt->dqio_mutex (VFS Quota Mutex)
      - qtree_read_dquot
       - f2fs_quota_read
        - read_mapping_page (GFP_KERNEL / allows GFP_FS)
         - __alloc_pages_nodemask
          - try_to_free_pages (Direct Reclaim)
           - prune_icache_sb
            - evict
             - f2fs_evict_inode
              - dquot_drop
               - dqput
                - dquot_commit
                 : tries to lock &dqopt->dqio_mutex again
                 ==> DEADLOCK (waiting for itself)

As Jan Kara mentioned, quota system has fixed this issue w/ commit
537e11cdc7a6 ("quota: Prevent memory allocation recursion while holding
dq_lock"), so this GFP_NOFS flag should be relic, let's use GFP_KERNEL
instead.

Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Chao Yu <chao@kernel.org>
---
v2:
- fix to use GFP_KERNEL instead of 0.
 fs/f2fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index da468df058eb..b1725ca68010 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3168,7 +3168,7 @@ static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data,
 
 repeat:
 		folio = mapping_read_folio_gfp(mapping, off >> PAGE_SHIFT,
-				GFP_NOFS);
+				GFP_KERNEL);
 		if (IS_ERR(folio)) {
 			if (PTR_ERR(folio) == -ENOMEM) {
 				memalloc_retry_wait(GFP_NOFS);
-- 
2.49.0



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