The patch titled nfs: remove redundant tests on reading new pages has been added to the -mm tree. Its filename is nfs-remove-redundant-tests-on-reading-new-pages.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this 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 linux-next.patch 9p-convert-d_iname-references-to-d_namename.patch nfs-remove-redundant-tests-on-reading-new-pages.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html