It is possible for file-backed pages to end up in a contiguous memory area (CMA), such that the relevant page must be migrated using the .migratepage() callback when its backing physical memory is selected for use in an CMA allocation (through cma_alloc()). However, if a set of address space operations (AOPs) for a file-backed page lacks a migratepage() page call-back, fallback_migrate_page() will be used instead, which through try_to_release_page() calls try_to_free_buffers() (which is called directly or through a try_to_free_buffers() callback. try_to_free_buffers() in turn calls drop_buffers(). drop_buffers() itself can fail due to the buffer_head associated with a page being busy. However, it is possible that the buffer_head is on an LRU list for a CPU, such that we can try removing the buffer_head from that list, in order to successfully release the page. Do this. For reference ext4_journalled_aops is a set of AOPs that lacks the migratepage() callback. Laura Abbott (1): fs/buffer.c: Revoke LRU when trying to drop buffers fs/buffer.c | 47 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 45 insertions(+), 2 deletions(-) -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
