mm: use memalloc_nofs_save() in page_cache_ra_order()

In the Linux kernel, the following vulnerability has been resolved:

mm: use memalloc_nofs_save() in page_cache_ra_order()

See commit f2c817bed58d ("mm: use memalloc_nofs_save in readahead path"),

ensure that page_cache_ra_order() do not attempt to reclaim file-backed

pages too, or it leads to a deadlock, found issue when test ext4 large

folio.

INFO: task DataXceiver for:7494 blocked for more than 120 seconds.

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:DataXceiver for state:D stack:0 pid:7494 ppid:1 flags:0x00000200

Call trace:

__switch_to+0x14c/0x240

__schedule+0x82c/0xdd0

schedule+0x58/0xf0

io_schedule+0x24/0xa0

__folio_lock+0x130/0x300

migrate_pages_batch+0x378/0x918

migrate_pages+0x350/0x700

compact_zone+0x63c/0xb38

compact_zone_order+0xc0/0x118

try_to_compact_pages+0xb0/0x280

__alloc_pages_direct_compact+0x98/0x248

__alloc_pages+0x510/0x1110

alloc_pages+0x9c/0x130

folio_alloc+0x20/0x78

filemap_alloc_folio+0x8c/0x1b0

page_cache_ra_order+0x174/0x308

ondemand_readahead+0x1c8/0x2b8

page_cache_async_ra+0x68/0xb8

filemap_readahead.isra.0+0x64/0xa8

filemap_get_pages+0x3fc/0x5b0

filemap_splice_read+0xf4/0x280

ext4_file_splice_read+0x2c/0x48 [ext4]

vfs_splice_read.part.0+0xa8/0x118

splice_direct_to_actor+0xbc/0x288

do_splice_direct+0x9c/0x108

do_sendfile+0x328/0x468

__arm64_sys_sendfile64+0x8c/0x148

invoke_syscall+0x4c/0x118

el0_svc_common.constprop.0+0xc8/0xf0

do_el0_svc+0x24/0x38

el0_svc+0x4c/0x1f8

el0t_64_sync_handler+0xc0/0xc8

el0t_64_sync+0x188/0x190