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erofs: fix missing xas_retry() in fscache mode

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The xarray iteration only holds the RCU read lock and thus may encounter
XA_RETRY_ENTRY if there's process modifying the xarray concurrently.
This will cause oops when referring to the invalid entry.

Fix this by adding the missing xas_retry(), which will make the
iteration wind back to the root node if XA_RETRY_ENTRY is encountered.

Fixes: d435d53228 ("erofs: change to use asynchronous io for fscache readpage/readahead")
Suggested-by: David Howells <dhowells@redhat.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221114121943.29987-1-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Jingbo Xu 2022-11-14 20:19:43 +08:00 committed by Gao Xiang
parent 39bfcb8138
commit 37020bbb71
1 changed files with 7 additions and 3 deletions
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10
fs/erofs/fscache.c
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@ -75,11 +75,15 @@ static void erofs_fscache_rreq_unlock_folios(struct netfs_io_request *rreq)
rcu_read_lock(); rcu_read_lock();
xas_for_each(&xas, folio, last_page) { xas_for_each(&xas, folio, last_page) {
unsigned int pgpos = unsigned int pgpos, pgend;
(folio_index(folio) - start_page) * PAGE_SIZE;
unsigned int pgend = pgpos + folio_size(folio);
bool pg_failed = false; bool pg_failed = false;
if (xas_retry(&xas, folio))
continue;
pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
pgend = pgpos + folio_size(folio);
for (;;) { for (;;) {
if (!subreq) { if (!subreq) {
pg_failed = true; pg_failed = true;