From da0386c1c70da1a01b5fa8ec503b96116bc8734c Mon Sep 17 00:00:00 2001 From: Boris Burkov Date: Tue, 2 Jul 2024 07:31:13 -0700 Subject: [PATCH] btrfs: fix folio refcount in btrfs_do_encoded_write() The conversion to folios switched __free_page() to __folio_put() in the error path in btrfs_do_encoded_write(). However, this gets the page refcounting wrong. If we do hit that error path (I reproduced by modifying btrfs_do_encoded_write to pretend to always fail in a way that jumps to out_folios and running the fstests case btrfs/281), then we always hit the following BUG freeing the folio: BUG: Bad page state in process btrfs pfn:40ab0b page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x61be5 pfn:0x40ab0b flags: 0x5ffff0000000000(node=0|zone=2|lastcpupid=0x1ffff) raw: 05ffff0000000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000061be5 0000000000000000 00000001ffffffff 0000000000000000 page dumped because: nonzero _refcount Call Trace: dump_stack_lvl+0x3d/0xe0 bad_page+0xea/0xf0 free_unref_page+0x8e1/0x900 ? __mem_cgroup_uncharge+0x69/0x90 __folio_put+0xe6/0x190 btrfs_do_encoded_write+0x445/0x780 ? current_time+0x25/0xd0 btrfs_do_write_iter+0x2cc/0x4b0 btrfs_ioctl_encoded_write+0x2b6/0x340 It turns out __free_page() decreases the page reference count while __folio_put() does not. Switch __folio_put() to folio_put() which decreases the folio reference count first. Fixes: 400b172b8cdc ("btrfs: compression: migrate compression/decompression paths to folios") Tested-by: Ed Tomlinson Reviewed-by: Qu Wenruo Reviewed-by: Filipe Manana Signed-off-by: Boris Burkov Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index d0274324c75a0d..6c96a6086d3fdb 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -10382,7 +10382,7 @@ ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from, out_folios: for (i = 0; i < nr_folios; i++) { if (folios[i]) - __folio_put(folios[i]); + folio_put(folios[i]); } kvfree(folios); out: