The patch titled
nfs: remove redundant tests on reading new pages
has been removed from the -mm tree. Its filename was
nfs-remove-redundant-tests-on-reading-new-pages.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: nfs: remove redundant tests on reading new pages
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
aops->readpages() and its NFS helper readpage_async_filler() will only be
called to do readahead I/O for newly allocated pages. So it's not
necessary to test for the always 0 dirty/uptodate page flags.
The removal of nfs_wb_page() call also fixes a readahead bug: the NFS
readahead has been synchronous since 2.6.23, because that call will clear
PG_readahead, which is the reminder for asynchronous readahead.
More background: the PG_readahead page flag is shared with PG_reclaim, one
for read path and the other for write path. clear_page_dirty_for_io()
unconditionally clears PG_readahead to prevent possible readahead
residuals, assuming itself to be always called in the write path.
However, NFS is one and the only exception in that it _always_ calls
clear_page_dirty_for_io() in the read path, i.e. for
readpages()/readpage().
This bug was found when playing with my readahead tracing module posted at
http://lkml.org/lkml/2008/11/27/373 and confirmed to work.
The NFS readahead traces are now
[ 59.972526] readahead-initial0(pid=3646(dd), dev=00:0f(0:f), ino=293189(1G), req=0+25, ra=0+60-30, async=0) = 60
[ 59.992734] readahead-subsequent(pid=3646(dd), dev=00:0f(0:f), ino=293189(1G), req=30+20, ra=60+30-30, async=1) = 30
[ 60.030900] readahead-subsequent(pid=3646(dd), dev=00:0f(0:f), ino=293189(1G), req=60+15, ra=90+30-30, async=1) = 30
[ 60.031687] readahead-subsequent(pid=3646(dd), dev=00:0f(0:f), ino=293189(1G), req=90+10, ra=120+30-30, async=1) = 30
The async field was always 0 before this patch.
On the trace messages: they are generated by the command
'dd if=/tmp/sparse/1G of=/dev/null bs=100k count=9' with readahead_size=120k.
The printk for generating the messages is:
printk(KERN_DEBUG "readahead-%s(pid=%d(%s), dev=%02x:%02x(%s), "
"ino=%lu(%s), req=%lu+%lu, ra=%lu+%d-%d, async=%d) = %d\n",
ra_pattern_names[pattern],
current->pid, current->comm,
MAJOR(mapping->host->i_sb->s_dev),
MINOR(mapping->host->i_sb->s_dev),
mapping->host->i_sb->s_id,
mapping->host->i_ino,
filp->f_path.dentry->d_name.name,
offset, req_size,
ra->start, ra->size, ra->async_size,
async,
actual);
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxx>
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nfs/read.c | 6 ------
1 file changed, 6 deletions(-)
diff -puN fs/nfs/read.c~nfs-remove-redundant-tests-on-reading-new-pages fs/nfs/read.c
--- a/fs/nfs/read.c~nfs-remove-redundant-tests-on-reading-new-pages
+++ a/fs/nfs/read.c
@@ -533,12 +533,6 @@ readpage_async_filler(void *data, struct
unsigned int len;
int error;
- error = nfs_wb_page(inode, page);
- if (error)
- goto out_unlock;
- if (PageUptodate(page))
- goto out_unlock;
-
len = nfs_page_length(page);
if (len == 0)
return nfs_return_empty_page(page);
_
Patches currently in -mm which might be from fengguang.wu@xxxxxxxxx are
origin.patch
linux-next.patch
generic-swap-sparc-rename-swap-to-swap_ulong.patch
generic-swap-iphase-rename-swap-to-swap_byte_order.patch
generic-swap-lib-sortc-rename-swap-to-swap_func.patch
generic-swap-introduce-global-macro-swapa-b.patch
generic-swap-ext3-remove-local-swap-macro.patch
generic-swap-ext4-remove-local-swap-macro.patch
generic-swap-sched-remove-local-swap-macro.patch
generic-swap-dcache-use-swap-instead-of-private-do_switch.patch
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