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Message-ID: <20091002144622.GA29123@localhost>
Date: Fri, 2 Oct 2009 22:46:22 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Jan Kara <jack@...e.cz>
Cc: Theodore Tso <tytso@....edu>,
Christoph Hellwig <hch@...radead.org>,
Dave Chinner <david@...morbit.com>,
Chris Mason <chris.mason@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
"Li, Shaohua" <shaohua.li@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"richard@....demon.co.uk" <richard@....demon.co.uk>,
"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
linux-fsdevel@...r.kernel.org, Steve French <sfrench@...ba.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Mark Fasheh <mfasheh@...e.com>,
Joel Becker <joel.becker@...cle.com>,
David Howells <dhowells@...hat.com>,
Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [RFC] writeback: abort writeback of the inode on wrap-around
On Fri, Oct 02, 2009 at 05:50:50PM +0800, Wu Fengguang wrote:
>
> The new .stop_on_wrap is a quick hack to show the basic idea. Ideal
> would be to just convert the existing .range_cyclic to new behavior.
> This should simplify a lot of code.
>
> Since this involves many filesystems. I'd like to ask if any of them
> in fact _desire_ the current .range_cyclic semantics to wrap?
Here is the more complete patch, not tested yet :)
Convert wbc.range_cyclic to new behavior: when past EOF, abort the
writeback of the current inode, which will instruct
writeback_single_inode() to redirty_tail() it.
This is the right behavior for
- sync writeback (is already so with range_whole)
we have scanned the inode address space, and don't care any more newly
dirtied pages. So shall update its i_dirtied_when and exclude it from
the todo list.
- periodic writeback
any more newly dirtied pages should be associated with a new expire
time. This also prevents pointless IO for busy overwriters.
- background writeback
irrelevant because it generally don't care the dirty timestamp.
That should get rid of one ineffcient IO pattern of .range_cyclic when
writeback_index wraps, in which the submitted pages may be consisted of
two distant ranges: submit [10000-10100], (wrap), submit [0-100].
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
drivers/staging/pohmelfs/inode.c | 25 ++++++++-----------------
fs/afs/write.c | 21 +++------------------
fs/btrfs/extent_io.c | 21 ++++++---------------
fs/cifs/file.c | 15 +++------------
fs/ext4/inode.c | 18 ++++--------------
fs/gfs2/aops.c | 16 ++--------------
fs/nfs/write.c | 6 +++---
mm/page-writeback.c | 25 ++++---------------------
8 files changed, 33 insertions(+), 114 deletions(-)
--- linux.orig/mm/page-writeback.c 2009-10-02 22:06:49.000000000 +0800
+++ linux/mm/page-writeback.c 2009-10-02 22:31:26.000000000 +0800
@@ -789,29 +789,21 @@ int write_cache_pages(struct address_spa
int done = 0;
struct pagevec pvec;
int nr_pages;
- pgoff_t uninitialized_var(writeback_index);
pgoff_t index;
pgoff_t end; /* Inclusive */
pgoff_t done_index;
- int cycled;
int range_whole = 0;
long nr_to_write = wbc->nr_to_write;
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
- writeback_index = mapping->writeback_index; /* prev offset */
- index = writeback_index;
- if (index == 0)
- cycled = 1;
- else
- cycled = 0;
+ index = mapping->writeback_index; /* prev offset */
end = -1;
} else {
index = wbc->range_start >> PAGE_CACHE_SHIFT;
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- cycled = 1; /* ignore range_cyclic tests */
}
retry:
done_index = index;
@@ -821,8 +813,10 @@ retry:
nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY,
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
- if (nr_pages == 0)
+ if (nr_pages == 0) {
+ done_index = 0;
break;
+ }
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
@@ -919,17 +913,6 @@ continue_unlock:
pagevec_release(&pvec);
cond_resched();
}
- if (!cycled && !done) {
- /*
- * range_cyclic:
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- cycled = 1;
- index = 0;
- end = writeback_index - 1;
- goto retry;
- }
if (!wbc->no_nrwrite_index_update) {
if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
mapping->writeback_index = done_index;
--- linux.orig/drivers/staging/pohmelfs/inode.c 2009-10-02 22:06:45.000000000 +0800
+++ linux/drivers/staging/pohmelfs/inode.c 2009-10-02 22:17:41.000000000 +0800
@@ -149,7 +149,6 @@ static int pohmelfs_writepages(struct ad
int nr_pages;
pgoff_t index;
pgoff_t end; /* Inclusive */
- int scanned = 0;
int range_whole = 0;
if (wbc->range_cyclic) {
@@ -160,17 +159,18 @@ static int pohmelfs_writepages(struct ad
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
}
-retry:
+
while (!done && (index <= end)) {
unsigned int i = min(end - index, (pgoff_t)psb->trans_max_pages);
int path_len;
struct netfs_trans *trans;
err = pohmelfs_inode_has_dirty_pages(mapping, index);
- if (!err)
+ if (!err) {
+ index = 0;
break;
+ }
err = pohmelfs_path_length(pi);
if (err < 0)
@@ -197,15 +197,16 @@ retry:
dprintk("%s: t: %p, nr_pages: %u, end: %lu, index: %lu, max: %u.\n",
__func__, trans, nr_pages, end, index, trans->page_num);
- if (!nr_pages)
+ if (!nr_pages) {
+ index = 0;
goto err_out_reset;
+ }
err = pohmelfs_write_inode_create(inode, trans);
if (err)
goto err_out_reset;
err = 0;
- scanned = 1;
for (i = 0; i < trans->page_num; i++) {
struct page *page = trans->pages[i];
@@ -215,7 +216,7 @@ retry:
if (unlikely(page->mapping != mapping))
goto out_continue;
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
done = 1;
goto out_continue;
}
@@ -263,16 +264,6 @@ err_out_reset:
break;
}
- if (!scanned && !done) {
- /*
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- scanned = 1;
- index = 0;
- goto retry;
- }
-
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = index;
--- linux.orig/fs/afs/write.c 2009-10-02 22:11:40.000000000 +0800
+++ linux/fs/afs/write.c 2009-10-02 22:12:06.000000000 +0800
@@ -455,8 +455,6 @@ int afs_writepage(struct page *page, str
}
wbc->nr_to_write -= ret;
- if (wbc->nonblocking && bdi_write_congested(bdi))
- wbc->encountered_congestion = 1;
_leave(" = 0");
return 0;
@@ -479,8 +477,10 @@ static int afs_writepages_region(struct
do {
n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
1, &page);
- if (!n)
+ if (!n) {
+ index = 0;
break;
+ }
_debug("wback %lx", page->index);
@@ -529,11 +529,6 @@ static int afs_writepages_region(struct
wbc->nr_to_write -= ret;
- if (wbc->nonblocking && bdi_write_congested(bdi)) {
- wbc->encountered_congestion = 1;
- break;
- }
-
cond_resched();
} while (index < end && wbc->nr_to_write > 0);
@@ -554,20 +549,10 @@ int afs_writepages(struct address_space
_enter("");
- if (wbc->nonblocking && bdi_write_congested(bdi)) {
- wbc->encountered_congestion = 1;
- _leave(" = 0 [congest]");
- return 0;
- }
-
if (wbc->range_cyclic) {
start = mapping->writeback_index;
end = -1;
ret = afs_writepages_region(mapping, wbc, start, end, &next);
- if (start > 0 && wbc->nr_to_write > 0 && ret == 0 &&
- !(wbc->nonblocking && wbc->encountered_congestion))
- ret = afs_writepages_region(mapping, wbc, 0, start,
- &next);
mapping->writeback_index = next;
} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT);
--- linux.orig/fs/btrfs/extent_io.c 2009-10-02 22:06:37.000000000 +0800
+++ linux/fs/btrfs/extent_io.c 2009-10-02 22:25:29.000000000 +0800
@@ -2402,10 +2402,9 @@ static int extent_write_cache_pages(stru
int done = 0;
int nr_to_write_done = 0;
struct pagevec pvec;
- int nr_pages;
+ int nr_pages = 1;
pgoff_t index;
pgoff_t end; /* Inclusive */
- int scanned = 0;
int range_whole = 0;
pagevec_init(&pvec, 0);
@@ -2417,16 +2416,14 @@ static int extent_write_cache_pages(stru
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
}
-retry:
+
while (!done && !nr_to_write_done && (index <= end) &&
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY, min(end - index,
(pgoff_t)PAGEVEC_SIZE-1) + 1))) {
unsigned i;
- scanned = 1;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
@@ -2447,7 +2444,7 @@ retry:
continue;
}
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
done = 1;
unlock_page(page);
continue;
@@ -2484,15 +2481,9 @@ retry:
pagevec_release(&pvec);
cond_resched();
}
- if (!scanned && !done) {
- /*
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- scanned = 1;
- index = 0;
- goto retry;
- }
+ if (!nr_pages)
+ mapping->writeback_index = 0;
+
return ret;
}
--- linux.orig/fs/cifs/file.c 2009-10-02 22:06:45.000000000 +0800
+++ linux/fs/cifs/file.c 2009-10-02 22:24:52.000000000 +0800
@@ -1356,7 +1356,6 @@ static int cifs_writepages(struct addres
struct page *page;
struct pagevec pvec;
int rc = 0;
- int scanned = 0;
int xid, long_op;
cifs_sb = CIFS_SB(mapping->host->i_sb);
@@ -1390,9 +1389,8 @@ static int cifs_writepages(struct addres
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
}
-retry:
+
while (!done && (index <= end) &&
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY,
@@ -1425,7 +1423,7 @@ retry:
break;
}
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
done = 1;
unlock_page(page);
break;
@@ -1537,15 +1535,8 @@ retry:
pagevec_release(&pvec);
}
- if (!scanned && !done) {
- /*
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- scanned = 1;
+ if (!nr_pages)
index = 0;
- goto retry;
- }
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = index;
--- linux.orig/fs/ext4/inode.c 2009-10-02 22:06:45.000000000 +0800
+++ linux/fs/ext4/inode.c 2009-10-02 22:33:57.000000000 +0800
@@ -2805,7 +2805,7 @@ static int ext4_da_writepages(struct add
int pages_written = 0;
long pages_skipped;
unsigned int max_pages;
- int range_cyclic, cycled = 1, io_done = 0;
+ int range_cyclic, io_done = 0;
int needed_blocks, ret = 0;
long desired_nr_to_write, nr_to_writebump = 0;
loff_t range_start = wbc->range_start;
@@ -2840,8 +2840,6 @@ static int ext4_da_writepages(struct add
range_cyclic = wbc->range_cyclic;
if (wbc->range_cyclic) {
index = mapping->writeback_index;
- if (index)
- cycled = 0;
wbc->range_start = index << PAGE_CACHE_SHIFT;
wbc->range_end = LLONG_MAX;
wbc->range_cyclic = 0;
@@ -2889,7 +2887,6 @@ static int ext4_da_writepages(struct add
wbc->no_nrwrite_index_update = 1;
pages_skipped = wbc->pages_skipped;
-retry:
while (!ret && wbc->nr_to_write > 0) {
/*
@@ -2963,20 +2960,13 @@ retry:
wbc->pages_skipped = pages_skipped;
ret = 0;
io_done = 1;
- } else if (wbc->nr_to_write)
+ } else if (wbc->nr_to_write <= 0) {
/*
* There is no more writeout needed
- * or we requested for a noblocking writeout
- * and we found the device congested
*/
+ index = 0;
break;
- }
- if (!io_done && !cycled) {
- cycled = 1;
- index = 0;
- wbc->range_start = index << PAGE_CACHE_SHIFT;
- wbc->range_end = mapping->writeback_index - 1;
- goto retry;
+ }
}
if (pages_skipped != wbc->pages_skipped)
ext4_msg(inode->i_sb, KERN_CRIT,
--- linux.orig/fs/gfs2/aops.c 2009-10-02 22:06:45.000000000 +0800
+++ linux/fs/gfs2/aops.c 2009-10-02 22:36:09.000000000 +0800
@@ -287,7 +287,7 @@ static int gfs2_write_jdata_pagevec(stru
continue;
}
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
ret = 1;
unlock_page(page);
continue;
@@ -340,7 +340,6 @@ static int gfs2_write_cache_jdata(struct
int nr_pages;
pgoff_t index;
pgoff_t end;
- int scanned = 0;
int range_whole = 0;
pagevec_init(&pvec, 0);
@@ -352,15 +351,12 @@ static int gfs2_write_cache_jdata(struct
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
}
-retry:
while (!done && (index <= end) &&
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY,
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
- scanned = 1;
ret = gfs2_write_jdata_pagevec(mapping, wbc, &pvec, nr_pages, end);
if (ret)
done = 1;
@@ -371,16 +367,8 @@ retry:
cond_resched();
}
- if (!scanned && !done) {
- /*
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- scanned = 1;
+ if (!nr_pages)
index = 0;
- goto retry;
- }
-
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = index;
return ret;
--
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