fs/seq_file: fallback to vmalloc allocation There are a couple of seq_files which use the single_open() interface. This interface requires that the whole output must fit into a single buffer. E.g. for /proc/stat allocation failures have been observed because an order-4 memory allocation failed due to memory fragmentation. In such situations reading /proc/stat is not possible anymore. Therefore change the seq_file code to fallback to vmalloc allocations which will usually result in a couple of order-0 allocations and hence also work if memory is fragmented. For reference a call trace where reading from /proc/stat failed: sadc: page allocation failure: order:4, mode:0x1040d0 CPU: 1 PID: 192063 Comm: sadc Not tainted 3.10.0-123.el7.s390x #1 [...] Call Trace: show_stack+0x6c/0xe8 warn_alloc_failed+0xd6/0x138 __alloc_pages_nodemask+0x9da/0xb68 __get_free_pages+0x2e/0x58 kmalloc_order_trace+0x44/0xc0 stat_open+0x5a/0xd8 proc_reg_open+0x8a/0x140 do_dentry_open+0x1bc/0x2c8 finish_open+0x46/0x60 do_last+0x382/0x10d0 path_openat+0xc8/0x4f8 do_filp_open+0x46/0xa8 do_sys_open+0x114/0x1f0 sysc_tracego+0x14/0x1a Conflicts: fs/seq_file.c Bug: 17871993 Signed-off-by: Heiko Carstens Tested-by: David Rientjes Cc: Ian Kent Cc: Hendrik Brueckner Cc: Thorsten Diehl Cc: Andrea Righi Cc: Christoph Hellwig Cc: Al Viro Cc: Stefan Bader Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Git-commit: 058504edd02667eef8fac9be27ab3ea74332e9b4 Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git Change-Id: Iad795a92fee1983c300568429a6283c48625bd9a Signed-off-by: Jeremy Gebben Signed-off-by: Naveen Ramaraj

PS2: Fix MCFS #1

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