From: Sha Zhengju <handai....@taobao.com>
Commit a8e7d49a(Fix race in create_empty_buffers() vs
__set_page_dirty_buffers())
extracts TestSetPageDirty from __set_page_dirty and is far away from
account_page_dirtied.But it's better to make the two operations in one single
function to keep modular.So in order to avoid the potential race mentioned in
commit a8e7d49a, we can hold private_lock until __set_page_dirty completes.
I guess there's no deadlock between ->private_lock and ->tree_lock by quick
look.
It's a prepare patch for following memcg dirty page accounting patches.
Here is some test numbers that before/after this patch:
Test steps(Mem-24g, ext4):
drop_cache; sync
fio (buffered/randwrite/bs=4k/size=128m/filesize=1g/numjobs=8/sync)
We test it for 10 times and get the average numbers:
Before:
write: io=1024.0MB, bw=334678 KB/s, iops=83669.2 , runt= 3136 msec
lat (usec): min=1 , max=26203.1 , avg=81.473, stdev=275.754
After:
write: io=1024.0MB, bw=331583 KB/s, iops=82895.3 , runt= 3164.4 msec
lat (usec): min=1.1 , max=19001.6 , avg=83.544, stdev=272.704
Note that the impact is little(~1%).
Signed-off-by: Sha Zhengju <handai....@taobao.com>
Reviewed-by: Michal Hocko <mho...@suse.cz>
---
fs/buffer.c | 25 +++++++++++++------------
1 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index c7062c8..5e0b0d2 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -610,9 +610,15 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
* If warn is true, then emit a warning if the page is not uptodate and has
* not been truncated.
*/
-static void __set_page_dirty(struct page *page,
+static int __set_page_dirty(struct page *page,
struct address_space *mapping, int warn)
{
+ if (unlikely(!mapping))
+ return !TestSetPageDirty(page);
+
+ if (TestSetPageDirty(page))
+ return 0;
+
spin_lock_irq(&mapping->tree_lock);
if (page->mapping) { /* Race with truncate? */
WARN_ON_ONCE(warn && !PageUptodate(page));
@@ -622,6 +628,8 @@ static void __set_page_dirty(struct page *page,
}
spin_unlock_irq(&mapping->tree_lock);
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+
+ return 1;
}
/*
@@ -667,11 +675,9 @@ int __set_page_dirty_buffers(struct page *page)
bh = bh->b_this_page;
} while (bh != head);
}
- newly_dirty = !TestSetPageDirty(page);
+ newly_dirty = __set_page_dirty(page, mapping, 1);
spin_unlock(&mapping->private_lock);
- if (newly_dirty)
- __set_page_dirty(page, mapping, 1);
return newly_dirty;
}
EXPORT_SYMBOL(__set_page_dirty_buffers);
@@ -1119,14 +1125,9 @@ void mark_buffer_dirty(struct buffer_head *bh)
return;
}
- if (!test_set_buffer_dirty(bh)) {
- struct page *page = bh->b_page;
- if (!TestSetPageDirty(page)) {
- struct address_space *mapping = page_mapping(page);
- if (mapping)
- __set_page_dirty(page, mapping, 0);
- }
- }
+ if (!test_set_buffer_dirty(bh))
+ __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
+
}
EXPORT_SYMBOL(mark_buffer_dirty);
--
1.7.1
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