058504ed by Heiko Carstens Committed by Linus Torvalds

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

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: David Rientjes <rientjes@google.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Thorsten Diehl <thorsten.diehl@de.ibm.com>
Cc: Andrea Righi <andrea@betterlinux.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Stefan Bader <stefan.bader@canonical.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent f74373a5
...@@ -8,8 +8,10 @@ ...@@ -8,8 +8,10 @@
8 #include <linux/fs.h> 8 #include <linux/fs.h>
9 #include <linux/export.h> 9 #include <linux/export.h>
10 #include <linux/seq_file.h> 10 #include <linux/seq_file.h>
11 #include <linux/vmalloc.h>
11 #include <linux/slab.h> 12 #include <linux/slab.h>
12 #include <linux/cred.h> 13 #include <linux/cred.h>
14 #include <linux/mm.h>
13 15
14 #include <asm/uaccess.h> 16 #include <asm/uaccess.h>
15 #include <asm/page.h> 17 #include <asm/page.h>
...@@ -30,6 +32,16 @@ static void seq_set_overflow(struct seq_file *m) ...@@ -30,6 +32,16 @@ static void seq_set_overflow(struct seq_file *m)
30 m->count = m->size; 32 m->count = m->size;
31 } 33 }
32 34
35 static void *seq_buf_alloc(unsigned long size)
36 {
37 void *buf;
38
39 buf = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
40 if (!buf && size > PAGE_SIZE)
41 buf = vmalloc(size);
42 return buf;
43 }
44
33 /** 45 /**
34 * seq_open - initialize sequential file 46 * seq_open - initialize sequential file
35 * @file: file we initialize 47 * @file: file we initialize
...@@ -96,7 +108,7 @@ static int traverse(struct seq_file *m, loff_t offset) ...@@ -96,7 +108,7 @@ static int traverse(struct seq_file *m, loff_t offset)
96 return 0; 108 return 0;
97 } 109 }
98 if (!m->buf) { 110 if (!m->buf) {
99 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 111 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
100 if (!m->buf) 112 if (!m->buf)
101 return -ENOMEM; 113 return -ENOMEM;
102 } 114 }
...@@ -135,9 +147,9 @@ static int traverse(struct seq_file *m, loff_t offset) ...@@ -135,9 +147,9 @@ static int traverse(struct seq_file *m, loff_t offset)
135 147
136 Eoverflow: 148 Eoverflow:
137 m->op->stop(m, p); 149 m->op->stop(m, p);
138 kfree(m->buf); 150 kvfree(m->buf);
139 m->count = 0; 151 m->count = 0;
140 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 152 m->buf = seq_buf_alloc(m->size <<= 1);
141 return !m->buf ? -ENOMEM : -EAGAIN; 153 return !m->buf ? -ENOMEM : -EAGAIN;
142 } 154 }
143 155
...@@ -192,7 +204,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) ...@@ -192,7 +204,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
192 204
193 /* grab buffer if we didn't have one */ 205 /* grab buffer if we didn't have one */
194 if (!m->buf) { 206 if (!m->buf) {
195 m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); 207 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
196 if (!m->buf) 208 if (!m->buf)
197 goto Enomem; 209 goto Enomem;
198 } 210 }
...@@ -232,9 +244,9 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) ...@@ -232,9 +244,9 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
232 if (m->count < m->size) 244 if (m->count < m->size)
233 goto Fill; 245 goto Fill;
234 m->op->stop(m, p); 246 m->op->stop(m, p);
235 kfree(m->buf); 247 kvfree(m->buf);
236 m->count = 0; 248 m->count = 0;
237 m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); 249 m->buf = seq_buf_alloc(m->size <<= 1);
238 if (!m->buf) 250 if (!m->buf)
239 goto Enomem; 251 goto Enomem;
240 m->version = 0; 252 m->version = 0;
...@@ -350,7 +362,7 @@ EXPORT_SYMBOL(seq_lseek); ...@@ -350,7 +362,7 @@ EXPORT_SYMBOL(seq_lseek);
350 int seq_release(struct inode *inode, struct file *file) 362 int seq_release(struct inode *inode, struct file *file)
351 { 363 {
352 struct seq_file *m = file->private_data; 364 struct seq_file *m = file->private_data;
353 kfree(m->buf); 365 kvfree(m->buf);
354 kfree(m); 366 kfree(m);
355 return 0; 367 return 0;
356 } 368 }
...@@ -605,13 +617,13 @@ EXPORT_SYMBOL(single_open); ...@@ -605,13 +617,13 @@ EXPORT_SYMBOL(single_open);
605 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *), 617 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
606 void *data, size_t size) 618 void *data, size_t size)
607 { 619 {
608 char *buf = kmalloc(size, GFP_KERNEL); 620 char *buf = seq_buf_alloc(size);
609 int ret; 621 int ret;
610 if (!buf) 622 if (!buf)
611 return -ENOMEM; 623 return -ENOMEM;
612 ret = single_open(file, show, data); 624 ret = single_open(file, show, data);
613 if (ret) { 625 if (ret) {
614 kfree(buf); 626 kvfree(buf);
615 return ret; 627 return ret;
616 } 628 }
617 ((struct seq_file *)file->private_data)->buf = buf; 629 ((struct seq_file *)file->private_data)->buf = buf;
......