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9be23efacb
ceph_alloc_cap_flush() is called from ceph_writepages_start() inside
the writeback layer, where other allocations in the same path
(ceph_osdc_alloc_request, ceph_osdc_alloc_messages) already use
GFP_NOFS. A GFP_KERNEL allocation here can trigger direct reclaim
that recursively enters the filesystem writeback path:
ceph_writepages_start() // inode A writeback
ceph_alloc_cap_flush()
kmem_cache_alloc(..., GFP_KERNEL)
[direct reclaim]
try_to_free_pages()
shrink_slab()
super_cache_scan()
prune_icache_sb()
inode_lru_isolate()
iput() -> evict(inode_B)
[inode_B has dirty pages]
filemap_flush()
ceph_writepages_start() // re-enters writeback
ceph_alloc_cap_flush()
-> RECURSION / STACK OVERFLOW
All 11 callers of ceph_alloc_cap_flush() are in write or writeback
contexts: writepages (x2), write_iter, fallocate, copy_file_range,
setxattr, setattr, and page_mkwrite.
Signed-off-by: Xiubo Li <xiubo.li@clyso.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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