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-rw-r--r--mm/shmem.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 95e70e9ea060..fb76da93d369 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2147,6 +2147,10 @@ unlock:
* Looks up the page cache entry at @inode & @index. If a folio is
* present, it is returned locked with an increased refcount.
*
+ * If the caller modifies data in the folio, it must call folio_mark_dirty()
+ * before unlocking the folio to ensure that the folio is not reclaimed.
+ * There is no need to reserve space before calling folio_mark_dirty().
+ *
* When no folio is found, the behavior depends on @sgp:
* - for SGP_READ, *foliop is %NULL and 0 is returned
* - for SGP_NOALLOC, *foliop is %NULL and -ENOENT is returned