Home » Mailing lists » Devel » [PATCH] retries in ext3_prepare_write() violate ordering requirements
| [PATCH] retries in ext3_prepare_write() violate ordering requirements [message #8216] |
Fri, 10 November 2006 14:48  |
Kirill Korotaev
Messages: 137
Registered: January 2006
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Senior Member |
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in journal=ordered or journal=data mode retry in ext3_prepare_write()
breaks the requirements of journaling of data with respect to metadata.
The fix is to call commit_write to commit allocated zero blocks before
retry.
Author: Andrey Savochkin <saw@sw.ru>
Signed-Off-By: Kirill Korotaev <dev@openvz.org>
--- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
+++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
@@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
return ext3_journal_get_write_access(handle, bh);
}
+/*
+ * The idea of this helper function is following:
+ * if prepare_write has allocated some blocks, but not all of them, the
+ * transaction must include the content of the newly allocated blocks.
+ * This content is expected to be set to zeroes by block_prepare_write().
+ * 2006/10/14 SAW
+ */
+static int ext3_prepare_failure(struct file *file, struct page *page,
+ unsigned from, unsigned to)
+{
+ struct address_space *mapping;
+ struct buffer_head *bh, *head, *next;
+ unsigned block_start, block_end;
+ unsigned blocksize;
+
+ mapping = page->mapping;
+ if (ext3_should_writeback_data(mapping->host)) {
+ /* optimization: no constraints about data */
+skip:
+ ext3_journal_stop(ext3_journal_current_handle());
+ return 0;
+ }
+
+ head = page_buffers(page);
+ blocksize = head->b_size;
+ for ( bh = head, block_start = 0;
+ bh != head || !block_start;
+ block_start = block_end, bh = next)
+ {
+ next = bh->b_this_page;
+ block_end = block_start + blocksize;
+ if (block_end <= from)
+ continue;
+ if (block_start >= to) {
+ block_start = to;
+ break;
+ }
+ if (!buffer_mapped(bh))
+ break;
+ }
+ if (block_start <= from)
+ goto skip;
+
+ /* commit allocated and zeroed buffers */
+ return mapping->a_ops->commit_write(file, page, from, block_start);
+}
+
static int ext3_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
struct inode *inode = page->mapping->host;
- int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
+ int ret, ret2;
+ int needed_blocks = ext3_writepage_trans_blocks(inode);
handle_t *handle;
int retries = 0;
retry:
handle = ext3_journal_start(inode, needed_blocks);
- if (IS_ERR(handle)) {
- ret = PTR_ERR(handle);
- goto out;
- }
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
ret = nobh_prepare_write(page, from, to, ext3_get_block);
else
ret = block_prepare_write(page, from, to, ext3_get_block);
if (ret)
- goto prepare_write_failed;
+ goto failure;
if (ext3_should_journal_data(inode)) {
ret = walk_page_buffers(handle, page_buffers(page),
from, to, NULL, do_journal_get_write_access);
+ if (ret)
+ /* fatal error, just put the handle and return */
+ journal_stop(handle);
}
-prepare_write_failed:
- if (ret)
- ext3_journal_stop(handle);
+ return ret;
+
+failure:
+ ret2 = ext3_prepare_failure(file, page, from, to);
+ if (ret2 < 0)
+ return ret2;
if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
goto retry;
-out:
+ /* retry number exceeded, or other error like -EDQUOT */
return ret;
}
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| Re: [PATCH] retries in ext3_prepare_write() violate ordering requirements [message #8234 is a reply to message #8216] |
Fri, 10 November 2006 18:47  |
Andrew Morton
Messages: 127
Registered: December 2005
|
Senior Member |
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On Fri, 10 Nov 2006 17:55:53 +0300
Kirill Korotaev <dev@openvz.org> wrote:
> in journal=ordered or journal=data mode retry in ext3_prepare_write()
> breaks the requirements of journaling of data with respect to metadata.
> The fix is to call commit_write to commit allocated zero blocks before
> retry.
>
How was this problem detected? (ie: why was block_prepare_write() failing?)
How was the patch tested?
Was nobh-mode also tested?
>
> --- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
> +++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
> @@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
> return ext3_journal_get_write_access(handle, bh);
> }
>
> +/*
> + * The idea of this helper function is following:
> + * if prepare_write has allocated some blocks, but not all of them, the
> + * transaction must include the content of the newly allocated blocks.
> + * This content is expected to be set to zeroes by block_prepare_write().
> + * 2006/10/14 SAW
> + */
> +static int ext3_prepare_failure(struct file *file, struct page *page,
> + unsigned from, unsigned to)
> +{
> + struct address_space *mapping;
> + struct buffer_head *bh, *head, *next;
> + unsigned block_start, block_end;
> + unsigned blocksize;
> +
> + mapping = page->mapping;
> + if (ext3_should_writeback_data(mapping->host)) {
> + /* optimization: no constraints about data */
> +skip:
> + ext3_journal_stop(ext3_journal_current_handle());
> + return 0;
Should this be `return ext3_journal_stop(...);'?
> + }
> +
> + head = page_buffers(page);
> + blocksize = head->b_size;
> + for ( bh = head, block_start = 0;
> + bh != head || !block_start;
> + block_start = block_end, bh = next)
> + {
> + next = bh->b_this_page;
> + block_end = block_start + blocksize;
> + if (block_end <= from)
> + continue;
> + if (block_start >= to) {
> + block_start = to;
> + break;
> + }
> + if (!buffer_mapped(bh))
> + break;
What is the significance of buffer_mapped() here? Outside EOF or into a
hole? If so, then block_start >= to, and we can't get here??
> + }
> + if (block_start <= from)
> + goto skip;
> +
> + /* commit allocated and zeroed buffers */
> + return mapping->a_ops->commit_write(file, page, from, block_start);
> +}
> +
> static int ext3_prepare_write(struct file *file, struct page *page,
> unsigned from, unsigned to)
> {
> struct inode *inode = page->mapping->host;
> - int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
> + int ret, ret2;
> + int needed_blocks = ext3_writepage_trans_blocks(inode);
> handle_t *handle;
> int retries = 0;
>
> retry:
> handle = ext3_journal_start(inode, needed_blocks);
> - if (IS_ERR(handle)) {
> - ret = PTR_ERR(handle);
> - goto out;
> - }
> + if (IS_ERR(handle))
> + return PTR_ERR(handle);
> if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
> ret = nobh_prepare_write(page, from, to, ext3_get_block);
> else
> ret = block_prepare_write(page, from, to, ext3_get_block);
> if (ret)
> - goto prepare_write_failed;
> + goto failure;
>
> if (ext3_should_journal_data(inode)) {
> ret = walk_page_buffers(handle, page_buffers(page),
> from, to, NULL, do_journal_get_write_access);
> + if (ret)
> + /* fatal error, just put the handle and return */
> + journal_stop(handle);
> }
> -prepare_write_failed:
> - if (ret)
> - ext3_journal_stop(handle);
> + return ret;
> +
> +failure:
> + ret2 = ext3_prepare_failure(file, page, from, to);
> + if (ret2 < 0)
> + return ret2;
> if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
> goto retry;
> -out:
> + /* retry number exceeded, or other error like -EDQUOT */
> return ret;
> }
>
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| Re: [PATCH] retries in ext3_prepare_write() violate ordering requirements [message #8279 is a reply to message #8234] |
Mon, 13 November 2006 12:32 |
dev
Messages: 1693
Registered: September 2005
Location: Moscow
|
Senior Member |
|
|
Andrew,
>>in journal=ordered or journal=data mode retry in ext3_prepare_write()
>>breaks the requirements of journaling of data with respect to metadata.
>>The fix is to call commit_write to commit allocated zero blocks before
>>retry.
>>
>
>
> How was this problem detected? (ie: why was block_prepare_write() failing?)
purely theoretically while hunting for other bugs related to ext3 and quota.
block_prepare_write() can fail e.g. if quota returns -EDQUOT in ext3_alloc_blocks().
> How was the patch tested?
1. it was tested as part of OpenVZ kernel
2. there were ext3 stress test done with lots of disk activity by Dmitry Monakhov.
> Was nobh-mode also tested?
I will ask to perform some more tests 100% triggering ext3_prepare_failure()
and with NOBH mode.
Thanks,
Kirill
>>--- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
>>+++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
>>@@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
>> return ext3_journal_get_write_access(handle, bh);
>> }
>>
>>+/*
>>+ * The idea of this helper function is following:
>>+ * if prepare_write has allocated some blocks, but not all of them, the
>>+ * transaction must include the content of the newly allocated blocks.
>>+ * This content is expected to be set to zeroes by block_prepare_write().
>>+ * 2006/10/14 SAW
>>+ */
>>+static int ext3_prepare_failure(struct file *file, struct page *page,
>>+ unsigned from, unsigned to)
>>+{
>>+ struct address_space *mapping;
>>+ struct buffer_head *bh, *head, *next;
>>+ unsigned block_start, block_end;
>>+ unsigned blocksize;
>>+
>>+ mapping = page->mapping;
>>+ if (ext3_should_writeback_data(mapping->host)) {
>>+ /* optimization: no constraints about data */
>>+skip:
>>+ ext3_journal_stop(ext3_journal_current_handle());
>>+ return 0;
>
>
> Should this be `return ext3_journal_stop(...);'?
>
>
>>+ }
>>+
>>+ head = page_buffers(page);
>>+ blocksize = head->b_size;
>>+ for ( bh = head, block_start = 0;
>>+ bh != head || !block_start;
>>+ block_start = block_end, bh = next)
>>+ {
>>+ next = bh->b_this_page;
>>+ block_end = block_start + blocksize;
>>+ if (block_end <= from)
>>+ continue;
>>+ if (block_start >= to) {
>>+ block_start = to;
>>+ break;
>>+ }
>>+ if (!buffer_mapped(bh))
>>+ break;
>
>
> What is the significance of buffer_mapped() here? Outside EOF or into a
> hole? If so, then block_start >= to, and we can't get here??
>
>
>>+ }
>>+ if (block_start <= from)
>>+ goto skip;
>>+
>>+ /* commit allocated and zeroed buffers */
>>+ return mapping->a_ops->commit_write(file, page, from, block_start);
>>+}
>>+
>> static int ext3_prepare_write(struct file *file, struct page *page,
>> unsigned from, unsigned to)
>> {
>> struct inode *inode = page->mapping->host;
>>- int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
>>+ int ret, ret2;
>>+ int needed_blocks = ext3_writepage_trans_blocks(inode);
>> handle_t *handle;
>> int retries = 0;
>>
>> retry:
>> handle = ext3_journal_start(inode, needed_blocks);
>>- if (IS_ERR(handle)) {
>>- ret = PTR_ERR(handle);
>>- goto out;
>>- }
>>+ if (IS_ERR(handle))
>>+ return PTR_ERR(handle);
>> if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
>> ret = nobh_prepare_write(page, from, to, ext3_get_block);
>> else
>> ret = block_prepare_write(page, from, to, ext3_get_block);
>> if (ret)
>>- goto prepare_write_failed;
>>+ goto failure;
>>
>> if (ext3_should_journal_data(inode)) {
>> ret = walk_page_buffers(handle, page_buffers(page),
>> from, to, NULL, do_journal_get_write_access);
>>+ if (ret)
>>+ /* fatal error, just put the handle and return */
>>+ journal_stop(handle);
>> }
>>-prepare_write_failed:
>>- if (ret)
>>- ext3_journal_stop(handle);
>>+ return ret;
>>+
>>+failure:
>>+ ret2 = ext3_prepare_failure(file, page, from, to);
>>+ if (ret2 < 0)
>>+ return ret2;
>> if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
>> goto retry;
>>-out:
>>+ /* retry number exceeded, or other error like -EDQUOT */
>> return ret;
>> }
>>
>
>
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| Re: [PATCH] retries in ext3_prepare_write() violate ordering requirements [message #8300 is a reply to message #8279] |
Tue, 14 November 2006 09:12 |
Kirill Korotaev
Messages: 137
Registered: January 2006
|
Senior Member |
|
|
Andrew,
Dmitry confirmed that it works in NOBH mode as well
and when quota limit is hit.
Thanks,
Kirill
> Andrew,
>
>
>>>in journal=ordered or journal=data mode retry in ext3_prepare_write()
>>>breaks the requirements of journaling of data with respect to metadata.
>>>The fix is to call commit_write to commit allocated zero blocks before
>>>retry.
>>>
>>
>>
>>How was this problem detected? (ie: why was block_prepare_write() failing?)
>
> purely theoretically while hunting for other bugs related to ext3 and quota.
> block_prepare_write() can fail e.g. if quota returns -EDQUOT in ext3_alloc_blocks().
>
>
>>How was the patch tested?
>
> 1. it was tested as part of OpenVZ kernel
> 2. there were ext3 stress test done with lots of disk activity by Dmitry Monakhov.
>
>
>>Was nobh-mode also tested?
>
> I will ask to perform some more tests 100% triggering ext3_prepare_failure()
> and with NOBH mode.
>
> Thanks,
> Kirill
>
>
>
>>>--- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
>>>+++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
>>>@@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
>>> return ext3_journal_get_write_access(handle, bh);
>>>}
>>>
>>>+/*
>>>+ * The idea of this helper function is following:
>>>+ * if prepare_write has allocated some blocks, but not all of them, the
>>>+ * transaction must include the content of the newly allocated blocks.
>>>+ * This content is expected to be set to zeroes by block_prepare_write().
>>>+ * 2006/10/14 SAW
>>>+ */
>>>+static int ext3_prepare_failure(struct file *file, struct page *page,
>>>+ unsigned from, unsigned to)
>>>+{
>>>+ struct address_space *mapping;
>>>+ struct buffer_head *bh, *head, *next;
>>>+ unsigned block_start, block_end;
>>>+ unsigned blocksize;
>>>+
>>>+ mapping = page->mapping;
>>>+ if (ext3_should_writeback_data(mapping->host)) {
>>>+ /* optimization: no constraints about data */
>>>+skip:
>>>+ ext3_journal_stop(ext3_journal_current_handle());
>>>+ return 0;
>>
>>
>>Should this be `return ext3_journal_stop(...);'?
>>
>>
>>
>>>+ }
>>>+
>>>+ head = page_buffers(page);
>>>+ blocksize = head->b_size;
>>>+ for ( bh = head, block_start = 0;
>>>+ bh != head || !block_start;
>>>+ block_start = block_end, bh = next)
>>>+ {
>>>+ next = bh->b_this_page;
>>>+ block_end = block_start + blocksize;
>>>+ if (block_end <= from)
>>>+ continue;
>>>+ if (block_start >= to) {
>>>+ block_start = to;
>>>+ break;
>>>+ }
>>>+ if (!buffer_mapped(bh))
>>>+ break;
>>
>>
>>What is the significance of buffer_mapped() here? Outside EOF or into a
>>hole? If so, then block_start >= to, and we can't get here??
>>
>>
>>
>>>+ }
>>>+ if (block_start <= from)
>>>+ goto skip;
>>>+
>>>+ /* commit allocated and zeroed buffers */
>>>+ return mapping->a_ops->commit_write(file, page, from, block_start);
>>>+}
>>>+
>>>static int ext3_prepare_write(struct file *file, struct page *page,
>>> unsigned from, unsigned to)
>>>{
>>> struct inode *inode = page->mapping->host;
>>>- int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
>>>+ int ret, ret2;
>>>+ int needed_blocks = ext3_writepage_trans_blocks(inode);
>>> handle_t *handle;
>>> int retries = 0;
>>>
>>>retry:
>>> handle = ext3_journal_start(inode, needed_blocks);
>>>- if (IS_ERR(handle)) {
>>>- ret = PTR_ERR(handle);
>>>- goto out;
>>>- }
>>>+ if (IS_ERR(handle))
>>>+ return PTR_ERR(handle);
>>> if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
>>> ret = nobh_prepare_write(page, from, to, ext3_get_block);
>>> else
>>> ret = block_prepare_write(page, from, to, ext3_get_block);
>>> if (ret)
>>>- goto prepare_write_failed;
>>>+ goto failure;
>>>
>>> if (ext3_should_journal_data(inode)) {
>>> ret = walk_page_buffers(handle, page_buffers(page),
>>> from, to, NULL, do_journal_get_write_access);
>>>+ if (ret)
>>>+ /* fatal error, just put the handle and return */
>>>+ journal_stop(handle);
>>> }
>>>-prepare_write_failed:
>>>- if (ret)
>>>- ext3_journal_stop(handle);
>>>+ return ret;
>>>+
>>>+failure:
>>>+ ret2 = ext3_prepare_failure(file, page, from, to);
>>>+ if (ret2 < 0)
>>>+ return ret2;
>>> if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
>>> goto retry;
>>>-out:
>>>+ /* retry number exceeded, or other error like -EDQUOT */
>>> return ret;
>>>}
>>>
>>
>>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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| Re: [PATCH] retries in ext3_prepare_write() violate ordering requirements [message #8365 is a reply to message #8234] |
Fri, 17 November 2006 13:58 |
Kirill Korotaev
Messages: 137
Registered: January 2006
|
Senior Member |
|
|
Andrew,
answers on your questions.
>>in journal=ordered or journal=data mode retry in ext3_prepare_write()
>>breaks the requirements of journaling of data with respect to metadata.
>>The fix is to call commit_write to commit allocated zero blocks before
>>retry.
>>
>
>
> How was this problem detected? (ie: why was block_prepare_write() failing?)
>
> How was the patch tested?
>
> Was nobh-mode also tested?
with nobh block size can't be less than page size, so all the problems
with retries disappear and our code will be a no-op.
>>--- ./fs/ext3/inode.c.ext3pw 2006-11-08 17:44:14.000000000 +0300
>>+++ ./fs/ext3/inode.c 2006-11-08 17:48:59.000000000 +0300
>>@@ -1148,37 +1148,89 @@ static int do_journal_get_write_access(h
>> return ext3_journal_get_write_access(handle, bh);
>> }
>>
>>+/*
>>+ * The idea of this helper function is following:
>>+ * if prepare_write has allocated some blocks, but not all of them, the
>>+ * transaction must include the content of the newly allocated blocks.
>>+ * This content is expected to be set to zeroes by block_prepare_write().
>>+ * 2006/10/14 SAW
>>+ */
>>+static int ext3_prepare_failure(struct file *file, struct page *page,
>>+ unsigned from, unsigned to)
>>+{
>>+ struct address_space *mapping;
>>+ struct buffer_head *bh, *head, *next;
>>+ unsigned block_start, block_end;
>>+ unsigned blocksize;
>>+
>>+ mapping = page->mapping;
>>+ if (ext3_should_writeback_data(mapping->host)) {
>>+ /* optimization: no constraints about data */
>>+skip:
>>+ ext3_journal_stop(ext3_journal_current_handle());
>>+ return 0;
>
>
> Should this be `return ext3_journal_stop(...);'?
will fix and send an incremental patch to you.
>>+ }
>>+
>>+ head = page_buffers(page);
>>+ blocksize = head->b_size;
>>+ for ( bh = head, block_start = 0;
>>+ bh != head || !block_start;
>>+ block_start = block_end, bh = next)
>>+ {
>>+ next = bh->b_this_page;
>>+ block_end = block_start + blocksize;
>>+ if (block_end <= from)
>>+ continue;
>>+ if (block_start >= to) {
>>+ block_start = to;
>>+ break;
>>+ }
>>+ if (!buffer_mapped(bh))
<<<< /* prepare_write failed on this bh */
>>+ break;
<<<< lost here:
if (ext3_should_journal_data(inode)) {
ret = do_journal_get_write_access(XXX);
if (ret) {
journal_stop(handle);
return ret;
}
}
>
> What is the significance of buffer_mapped() here? Outside EOF or into a
> hole? If so, then block_start >= to, and we can't get here??
/*
* block_start here becomes the first block where the current iteration
* of prepare_write failed.
*/
>>+ }
>>+ if (block_start <= from)
>>+ goto skip;
>>+
>>+ /* commit allocated and zeroed buffers */
>>+ return mapping->a_ops->commit_write(file, page, from, block_start);
>>+}
>>+
>> static int ext3_prepare_write(struct file *file, struct page *page,
>> unsigned from, unsigned to)
>> {
>> struct inode *inode = page->mapping->host;
>>- int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
>>+ int ret, ret2;
>>+ int needed_blocks = ext3_writepage_trans_blocks(inode);
>> handle_t *handle;
>> int retries = 0;
>>
>> retry:
>> handle = ext3_journal_start(inode, needed_blocks);
>>- if (IS_ERR(handle)) {
>>- ret = PTR_ERR(handle);
>>- goto out;
>>- }
>>+ if (IS_ERR(handle))
>>+ return PTR_ERR(handle);
>> if (test_opt(inode->i_sb, NOBH) && ext3_should_writeback_data(inode))
>> ret = nobh_prepare_write(page, from, to, ext3_get_block);
>> else
>> ret = block_prepare_write(page, from, to, ext3_get_block);
>> if (ret)
>>- goto prepare_write_failed;
>>+ goto failure;
>>
>> if (ext3_should_journal_data(inode)) {
>> ret = walk_page_buffers(handle, page_buffers(page),
>> from, to, NULL, do_journal_get_write_access);
>>+ if (ret)
>>+ /* fatal error, just put the handle and return */
>>+ journal_stop(handle);
>> }
>>-prepare_write_failed:
>>- if (ret)
>>- ext3_journal_stop(handle);
>>+ return ret;
>>+
>>+failure:
>>+ ret2 = ext3_prepare_failure(file, page, from, to);
>>+ if (ret2 < 0)
>>+ return ret2;
>> if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
>> goto retry;
>>-out:
>>+ /* retry number exceeded, or other error like -EDQUOT */
>> return ret;
>> }
>>
Kirill
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