linux-kernel - [PATCH 23/23] vfs: Teach readahead to use the file_hotplug

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Date:	Mon,  1 Jun 2009 14:50:48 -0700
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-fsdevel@...r.kernel.org>,
	Hugh Dickins <hugh@...itas.com>, Tejun Heo <tj@...nel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Eric W. Biederman" <ebiederm@...well.aristanetworks.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: [PATCH 23/23] vfs: Teach readahead to use the file_hotplug_lock

From: Eric W. Biederman <ebiederm@...well.aristanetworks.com>

Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
---
 mm/filemap.c |   25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 379ff0b..5016aa5 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1402,16 +1402,23 @@ SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
 
 	ret = -EBADF;
 	file = fget(fd);
-	if (file) {
-		if (file->f_mode & FMODE_READ) {
-			struct address_space *mapping = file->f_mapping;
-			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
-			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
-			unsigned long len = end - start + 1;
-			ret = do_readahead(mapping, file, start, len);
-		}
-		fput(file);
+	if (!file)
+		goto out;
+
+	if (!(file->f_mode & FMODE_READ))
+		goto out_fput;
+
+	if (file_hotplug_read_trylock(file)) {
+		struct address_space *mapping = file->f_mapping;
+		pgoff_t start = offset >> PAGE_CACHE_SHIFT;
+		pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
+		unsigned long len = end - start + 1;
+		ret = do_readahead(mapping, file, start, len);
+		file_hotplug_read_unlock(file);
 	}
+out_fput:
+	fput(file);
+out:
 	return ret;
 }
 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
-- 
1.6.3.1.54.g99dd.dirty

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