Re: [PATCH] conditionalize some boring buffer_head checks

Jeff Garzik
2004-04-14T09:11:53Z

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Andrew Morton wrote:
> Jeff Garzik <jgarzik@pobox.com> wrote:
>
>>I would rather not kill the code in submit_bh() outright, just disable
>> it for non-filesystem developers.
>
>
> submit_bh() is a slowpath ;) The one in mark_buffer_dirty() will be called
> more often, possibly others. Kill!

Jens seems to like the debugging checks, so here's an alterna-patch.

Jeff

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===== arch/alpha/Kconfig 1.36 vs edited =====
--- 1.36/arch/alpha/Kconfig Sat Mar 20 13:29:54 2004
+++ edited/arch/alpha/Kconfig Wed Apr 14 04:58:08 2004
@@ -690,6 +690,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
endmenu

source "security/Kconfig"
===== arch/arm/Kconfig 1.53 vs edited =====
--- 1.53/arch/arm/Kconfig Thu Apr 8 15:41:09 2004
+++ edited/arch/arm/Kconfig Wed Apr 14 04:58:08 2004
@@ -724,6 +724,13 @@
you are concerned with the code size or don't want to see these
messages.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
# These options are only for real kernel hackers who want to get their hands dirty.
config DEBUG_LL
bool "Kernel low-level debugging functions"
===== arch/arm26/Kconfig 1.11 vs edited =====
--- 1.11/arch/arm26/Kconfig Mon Mar 1 10:52:18 2004
+++ edited/arch/arm26/Kconfig Wed Apr 14 04:58:08 2004
@@ -316,6 +316,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
# These options are only for real kernel hackers who want to get their hands dirty.
config DEBUG_LL
bool "Kernel low-level debugging functions"
===== arch/i386/Kconfig 1.116 vs edited =====
--- 1.116/arch/i386/Kconfig Mon Apr 12 13:54:45 2004
+++ edited/arch/i386/Kconfig Wed Apr 14 04:58:08 2004
@@ -1286,6 +1286,13 @@
If you say Y here, various routines which may sleep will become very
noisy if they are called with a spinlock held.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
help
===== arch/ia64/Kconfig 1.69 vs edited =====
--- 1.69/arch/ia64/Kconfig Mon Apr 12 21:50:46 2004
+++ edited/arch/ia64/Kconfig Wed Apr 14 04:58:08 2004
@@ -503,6 +503,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config SYSVIPC_COMPAT
bool
depends on COMPAT && SYSVIPC
===== arch/m68k/Kconfig 1.31 vs edited =====
--- 1.31/arch/m68k/Kconfig Thu Feb 26 06:25:58 2004
+++ edited/arch/m68k/Kconfig Wed Apr 14 04:58:08 2004
@@ -688,6 +688,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
endmenu

source "security/Kconfig"
===== arch/mips/Kconfig 1.24 vs edited =====
--- 1.24/arch/mips/Kconfig Fri Mar 19 01:04:54 2004
+++ edited/arch/mips/Kconfig Wed Apr 14 04:58:08 2004
@@ -1253,6 +1253,13 @@
If you say Y here, various routines which may sleep will become very
noisy if they are called with a spinlock held.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config RTC_DS1742
bool "DS1742 BRAM/RTC support"
depends on TOSHIBA_JMR3927 || TOSHIBA_RBTX4927
===== arch/parisc/Kconfig 1.28 vs edited =====
--- 1.28/arch/parisc/Kconfig Fri Mar 19 01:04:54 2004
+++ edited/arch/parisc/Kconfig Wed Apr 14 04:58:08 2004
@@ -222,6 +222,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
endmenu

source "security/Kconfig"
===== arch/ppc/Kconfig 1.57 vs edited =====
--- 1.57/arch/ppc/Kconfig Tue Mar 30 10:39:41 2004
+++ edited/arch/ppc/Kconfig Wed Apr 14 04:58:08 2004
@@ -1209,6 +1209,13 @@
debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config BOOTX_TEXT
bool "Support for early boot text console (BootX or OpenFirmware only)"
depends PPC_OF
===== arch/ppc64/Kconfig 1.52 vs edited =====
--- 1.52/arch/ppc64/Kconfig Mon Apr 12 13:54:05 2004
+++ edited/arch/ppc64/Kconfig Wed Apr 14 04:58:08 2004
@@ -395,6 +395,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
endmenu

source "security/Kconfig"
===== arch/s390/Kconfig 1.25 vs edited =====
--- 1.25/arch/s390/Kconfig Fri Mar 19 01:04:54 2004
+++ edited/arch/s390/Kconfig Wed Apr 14 04:58:08 2004
@@ -397,6 +397,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config DEBUG_SPINLOCK_SLEEP
bool "Sleep-inside-spinlock checking"
help
===== arch/sparc/Kconfig 1.28 vs edited =====
--- 1.28/arch/sparc/Kconfig Fri Mar 19 01:04:54 2004
+++ edited/arch/sparc/Kconfig Wed Apr 14 04:58:08 2004
@@ -448,6 +448,13 @@
of the BUG call as well as the EIP and oops trace. This aids
debugging but costs about 70-100K of memory.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
endmenu

source "security/Kconfig"
===== arch/sparc64/Kconfig 1.50 vs edited =====
--- 1.50/arch/sparc64/Kconfig Fri Mar 19 01:04:54 2004
+++ edited/arch/sparc64/Kconfig Wed Apr 14 04:58:08 2004
@@ -679,6 +679,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config STACK_DEBUG
depends on DEBUG_KERNEL
bool "Stack Overflow Detection Support"
===== arch/um/Kconfig 1.14 vs edited =====
--- 1.14/arch/um/Kconfig Mon Apr 12 13:53:57 2004
+++ edited/arch/um/Kconfig Wed Apr 14 04:58:08 2004
@@ -233,6 +233,13 @@
If you're truly short on disk space or don't expect to report any
bugs back to the UML developers, say N, otherwise say Y.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config FRAME_POINTER
bool
default y if DEBUG_INFO
===== arch/v850/Kconfig 1.21 vs edited =====
--- 1.21/arch/v850/Kconfig Mon Feb 16 19:42:32 2004
+++ edited/arch/v850/Kconfig Wed Apr 14 04:58:08 2004
@@ -320,6 +320,13 @@
Say Y here only if you plan to use gdb to debug the kernel.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config MAGIC_SYSRQ
bool "Magic SysRq key"
depends on DEBUG_KERNEL
===== arch/x86_64/Kconfig 1.47 vs edited =====
--- 1.47/arch/x86_64/Kconfig Mon Apr 12 13:53:56 2004
+++ edited/arch/x86_64/Kconfig Wed Apr 14 04:58:08 2004
@@ -471,6 +471,13 @@
Please note that this option requires new binutils.
If you don't debug the kernel, you can say N.

+config DEBUG_BUFFERS
+ bool "Enable additional filesystem buffer_head checks"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, additional checks are performed that aid
+ filesystem development.
+
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
help
===== fs/buffer.c 1.237 vs edited =====
--- 1.237/fs/buffer.c Wed Apr 14 03:18:09 2004
+++ edited/fs/buffer.c Wed Apr 14 05:05:28 2004
@@ -55,6 +55,7 @@
* Debug/devel support stuff
*/

+#ifdef CONFIG_DEBUG_BUFFERS
void __buffer_error(char *file, int line)
{
static int enough;
@@ -69,6 +70,7 @@
dump_stack();
}
EXPORT_SYMBOL(__buffer_error);
+#endif /* CONFIG_DEBUG_BUFFERS */

inline void
init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
@@ -105,10 +107,9 @@
* waitqueue, which is used here. (Well. Other locked buffers
* against the page will pin it. But complain anyway).
*/
- if (atomic_read(&bh->b_count) == 0 &&
+ buffer_errchk (atomic_read(&bh->b_count) == 0 &&
!PageLocked(bh->b_page) &&
- !PageWriteback(bh->b_page))
- buffer_error();
+ !PageWriteback(bh->b_page));

clear_buffer_locked(bh);
smp_mb__after_clear_bit();
@@ -125,9 +126,8 @@
wait_queue_head_t *wqh = bh_waitq_head(bh);
DEFINE_WAIT(wait);

- if (atomic_read(&bh->b_count) == 0 &&
- (!bh->b_page || !PageLocked(bh->b_page)))
- buffer_error();
+ buffer_errchk(atomic_read(&bh->b_count) == 0 &&
+ (!bh->b_page || !PageLocked(bh->b_page)));

do {
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
@@ -146,8 +146,7 @@
static void
__set_page_buffers(struct page *page, struct buffer_head *head)
{
- if (page_has_buffers(page))
- buffer_error();
+ buffer_errchk(page_has_buffers(page));
page_cache_get(page);
SetPagePrivate(page);
page->private = (unsigned long)head;
@@ -433,7 +432,7 @@
}
bh = bh->b_this_page;
} while (bh != head);
- buffer_error();
+ BUG();
printk("block=%llu, b_blocknr=%llu\n",
(unsigned long long)block, (unsigned long long)bh->b_blocknr);
printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size);
@@ -847,10 +846,10 @@
struct buffer_head *bh = head;

do {
- if (buffer_uptodate(bh))
+ if (likely(buffer_uptodate(bh)))
set_buffer_dirty(bh);
else
- buffer_error();
+ BUG();
bh = bh->b_this_page;
} while (bh != head);
}
@@ -1151,7 +1150,7 @@
return page;

failed:
- buffer_error();
+ BUG();
unlock_page(page);
page_cache_release(page);
return NULL;
@@ -1247,8 +1246,7 @@
*/
void fastcall mark_buffer_dirty(struct buffer_head *bh)
{
- if (!buffer_uptodate(bh))
- buffer_error();
+ buffer_errchk(!buffer_uptodate(bh));
if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
__set_page_dirty_nobuffers(bh->b_page);
}
@@ -1267,7 +1265,7 @@
return;
}
printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
- buffer_error(); /* For the stack backtrace */
+ BUG();
}

/*
@@ -1294,8 +1292,7 @@
unlock_buffer(bh);
return bh;
} else {
- if (buffer_dirty(bh))
- buffer_error();
+ buffer_errchk(buffer_dirty(bh));
get_bh(bh);
bh->b_end_io = end_buffer_read_sync;
submit_bh(READ, bh);
@@ -1687,8 +1684,7 @@
old_bh = __find_get_block_slow(bdev, block, 0);
if (old_bh) {
#if 0 /* This happens. Later. */
- if (buffer_dirty(old_bh))
- buffer_error();
+ buffer_errchk(buffer_dirty(old_bh));
#endif
clear_buffer_dirty(old_bh);
wait_on_buffer(old_bh);
@@ -1737,8 +1733,7 @@
last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;

if (!page_has_buffers(page)) {
- if (!PageUptodate(page))
- buffer_error();
+ buffer_errchk(!PageUptodate(page));
create_empty_buffers(page, 1 << inode->i_blkbits,
(1 << BH_Dirty)|(1 << BH_Uptodate));
}
@@ -1768,8 +1763,7 @@
* this page can be outside i_size when there is a
* truncate in progress.
*
- * if (buffer_mapped(bh))
- * buffer_error();
+ * buffer_errchk(buffer_mapped(bh));
*/
/*
* The buffer was zeroed by block_write_full_page()
@@ -1777,8 +1771,7 @@
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
} else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
- if (buffer_new(bh))
- buffer_error();
+ buffer_errchk(buffer_new(bh));
err = get_block(inode, block, bh, 1);
if (err)
goto recover;
@@ -1811,8 +1804,7 @@
continue;
}
if (test_clear_buffer_dirty(bh)) {
- if (!buffer_uptodate(bh))
- buffer_error();
+ buffer_errchk(!buffer_uptodate(bh));
mark_buffer_async_write(bh);
} else {
unlock_buffer(bh);
@@ -1942,8 +1934,7 @@
unmap_underlying_metadata(bh->b_bdev,
bh->b_blocknr);
if (PageUptodate(page)) {
- if (!buffer_mapped(bh))
- buffer_error();
+ buffer_errchk(!buffer_mapped(bh));
set_buffer_uptodate(bh);
continue;
}
@@ -2001,8 +1992,7 @@
void *kaddr;

clear_buffer_new(bh);
- if (buffer_uptodate(bh))
- buffer_error();
+ buffer_errchk(buffer_uptodate(bh));
kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr+block_start, 0, bh->b_size);
kunmap_atomic(kaddr, KM_USER0);
@@ -2068,8 +2058,7 @@

if (!PageLocked(page))
PAGE_BUG(page);
- if (PageUptodate(page))
- buffer_error();
+ buffer_errchk(PageUptodate(page));
blocksize = 1 << inode->i_blkbits;
if (!page_has_buffers(page))
create_empty_buffers(page, blocksize, 0);
@@ -2692,12 +2681,9 @@
BUG_ON(!buffer_mapped(bh));
BUG_ON(!bh->b_end_io);

- if ((rw == READ || rw == READA) && buffer_uptodate(bh))
- buffer_error();
- if (rw == WRITE && !buffer_uptodate(bh))
- buffer_error();
- if (rw == READ && buffer_dirty(bh))
- buffer_error();
+ buffer_errchk((rw == READ || rw == READA) && buffer_uptodate(bh));
+ buffer_errchk(rw == WRITE && !buffer_uptodate(bh));
+ buffer_errchk(rw == READ && buffer_dirty(bh));

/* Only clear out a write error when rewriting */
if (test_set_buffer_req(bh) && rw == WRITE)
@@ -2807,7 +2793,7 @@
&& buffer_mapped(bh) /* discard_buffer */
&& S_ISBLK(page->mapping->host->i_mode))
{
- buffer_error();
+ BUG();
}
}
}
@@ -2857,8 +2843,7 @@
bh = bh->b_this_page;
} while (bh != head);

- if (!was_uptodate && PageUptodate(page) && !PageError(page))
- buffer_error();
+ buffer_errchk(!was_uptodate && PageUptodate(page) && !PageError(page));

do {
struct buffer_head *next = bh->b_this_page;
===== fs/mpage.c 1.54 vs edited =====
--- 1.54/fs/mpage.c Mon Apr 12 13:54:41 2004
+++ edited/fs/mpage.c Wed Apr 14 05:06:40 2004
@@ -485,8 +485,7 @@
break;
block_in_file++;
}
- if (page_block == 0)
- buffer_error();
+ buffer_errchk(page_block == 0);

first_unmapped = page_block;

===== fs/ext3/inode.c 1.90 vs edited =====
--- 1.90/fs/ext3/inode.c Tue Jan 20 20:58:53 2004
+++ edited/fs/ext3/inode.c Wed Apr 14 05:06:48 2004
@@ -1358,8 +1358,7 @@
}

if (!page_has_buffers(page)) {
- if (!PageUptodate(page))
- buffer_error();
+ buffer_errchk(!PageUptodate(page));
create_empty_buffers(page, inode->i_sb->s_blocksize,
(1 << BH_Dirty)|(1 << BH_Uptodate));
}
===== fs/ntfs/aops.c 1.96 vs edited =====
--- 1.96/fs/ntfs/aops.c Mon Apr 12 13:54:35 2004
+++ edited/fs/ntfs/aops.c Wed Apr 14 05:06:55 2004
@@ -1340,8 +1340,7 @@
void *kaddr;

clear_buffer_new(bh);
- if (buffer_uptodate(bh))
- buffer_error();
+ buffer_errchk(buffer_uptodate(bh));
kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr + block_start, 0, bh->b_size);
kunmap_atomic(kaddr, KM_USER0);
===== fs/reiserfs/inode.c 1.97 vs edited =====
--- 1.97/fs/reiserfs/inode.c Mon Apr 12 13:54:58 2004
+++ edited/fs/reiserfs/inode.c Wed Apr 14 05:07:16 2004
@@ -1924,10 +1924,8 @@
/* catch places below that try to log something without starting a trans */
th.t_trans_id = 0;

- if (!buffer_uptodate(bh_result)) {
- buffer_error();
+ if (!buffer_uptodate(bh_result))
return -EIO;
- }

kmap(bh_result->b_page) ;
start_over:
@@ -2057,8 +2055,7 @@
* in the BH_Uptodate is just a sanity check.
*/
if (!page_has_buffers(page)) {
- if (!PageUptodate(page))
- buffer_error();
+ buffer_errchk(!PageUptodate(page));
create_empty_buffers(page, inode->i_sb->s_blocksize,
(1 << BH_Dirty) | (1 << BH_Uptodate));
}
@@ -2120,8 +2117,7 @@
}
}
if (test_clear_buffer_dirty(bh)) {
- if (!buffer_uptodate(bh))
- buffer_error();
+ buffer_errchk(!buffer_uptodate(bh));
mark_buffer_async_write(bh);
} else {
unlock_buffer(bh);
===== include/linux/buffer_head.h 1.47 vs edited =====
--- 1.47/include/linux/buffer_head.h Wed Apr 14 03:18:09 2004
+++ edited/include/linux/buffer_head.h Wed Apr 14 05:08:07 2004
@@ -7,6 +7,7 @@
#ifndef _LINUX_BUFFER_HEAD_H
#define _LINUX_BUFFER_HEAD_H

+#include <linux/config.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/linkage.h>
@@ -65,8 +66,16 @@
* Debug
*/

+#ifdef CONFIG_DEBUG_BUFFERS
void __buffer_error(char *file, int line);
-#define buffer_error() __buffer_error(__FILE__, __LINE__)
+#define buffer_error(condition) \
+ do { \
+ if (unlikely(condition)) \
+ __buffer_error(__FILE__, __LINE__); \
+ } while (0)
+#else
+#define buffer_error(condition) do {} while (0)
+#endif

/*
* macro tricks to expand the set_buffer_foo(), clear_buffer_foo()