diff options
| author | Max Kellermann <max.kellermann@ionos.com> | 2025-04-29 01:09:33 +0200 |
|---|---|---|
| committer | Gao Xiang <xiang@kernel.org> | 2025-04-29 11:36:00 +0800 |
| commit | bbfe756dc3062c1e934f06e5ba39c239aa953b92 (patch) | |
| tree | 0751f97195bbb98608e621ff67de091268cc0ae5 /fs | |
| parent | 8d16dd7b651b75ce7c79da3539553a25e60668f5 (diff) | |
fs/erofs/fileio: call erofs_onlinefolio_split() after bio_add_folio()
If bio_add_folio() fails (because it is full),
erofs_fileio_scan_folio() needs to submit the I/O request via
erofs_fileio_rq_submit() and allocate a new I/O request with an empty
`struct bio`. Then it retries the bio_add_folio() call.
However, at this point, erofs_onlinefolio_split() has already been
called which increments `folio->private`; the retry will call
erofs_onlinefolio_split() again, but there will never be a matching
erofs_onlinefolio_end() call. This leaves the folio locked forever
and all waiters will be stuck in folio_wait_bit_common().
This bug has been added by commit ce63cb62d794 ("erofs: support
unencoded inodes for fileio"), but was practically unreachable because
there was room for 256 folios in the `struct bio` - until commit
9f74ae8c9ac9 ("erofs: shorten bvecs[] for file-backed mounts") which
reduced the array capacity to 16 folios.
It was now trivial to trigger the bug by manually invoking readahead
from userspace, e.g.:
posix_fadvise(fd, 0, st.st_size, POSIX_FADV_WILLNEED);
This should be fixed by invoking erofs_onlinefolio_split() only after
bio_add_folio() has succeeded. This is safe: asynchronous completions
invoking erofs_onlinefolio_end() will not unlock the folio because
erofs_fileio_scan_folio() is still holding a reference to be released
by erofs_onlinefolio_end() at the end.
Fixes: ce63cb62d794 ("erofs: support unencoded inodes for fileio")
Fixes: 9f74ae8c9ac9 ("erofs: shorten bvecs[] for file-backed mounts")
Cc: stable@vger.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Gao Xiang <xiang@kernel.org>
Tested-by: Hongbo Li <lihongbo22@huawei.com>
Link: https://lore.kernel.org/r/20250428230933.3422273-1-max.kellermann@ionos.com
Signed-off-by: Gao Xiang <xiang@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/erofs/fileio.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c index 4fa0a0121288..60c7cc4c105c 100644 --- a/fs/erofs/fileio.c +++ b/fs/erofs/fileio.c @@ -150,10 +150,10 @@ io_retry: io->rq->bio.bi_iter.bi_sector = io->dev.m_pa >> 9; attached = 0; } - if (!attached++) - erofs_onlinefolio_split(folio); if (!bio_add_folio(&io->rq->bio, folio, len, cur)) goto io_retry; + if (!attached++) + erofs_onlinefolio_split(folio); io->dev.m_pa += len; } cur += len; |