于 2011年11月23日 06:06, Andrew Morton 写道:
On Fri, 18 Nov 2011 18:39:50 +0800
Cong Wang<amwang@xxxxxxxxxx> wrote:
It seems that systemd needs tmpfs to support fallocate,
see http://lkml.org/lkml/2011/10/20/275. This patch adds
fallocate support to tmpfs.
As we already have shmem_truncate_range(), it is also easy
to add FALLOC_FL_PUNCH_HOLE support too.
...
+static long shmem_fallocate(struct file *file, int mode,
+ loff_t offset, loff_t len)
+{
+ struct inode *inode = file->f_path.dentry->d_inode;
+ pgoff_t start = offset>> PAGE_CACHE_SHIFT;
+ pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
+ pgoff_t index = start;
+ loff_t i_size = i_size_read(inode);
+ struct page *page = NULL;
+ int ret = 0;
+
+ mutex_lock(&inode->i_mutex);
It would be saner and less racy-looking to read i_size _after_ taking
i_mutex.
And if you do that, there's no need to use i_size_read() - just a plain
old
i_size = inode->i_size;
is OK.
Fair enough, I will fix that in V3.
Thanks, Andrew!
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