Re: 2.6.2-rc2 nfsd+xfs spins in i_size_read()

Andrew Morton
2004-01-30T23:12:05Z

Christoph Hellwig <hch@infradead.org> wrote:
>
> On Fri, Jan 30, 2004 at 02:34:59PM -0800, Andrew Morton wrote:
> > If two CPUs hit i_size_write() at the same time we have a bug. That
> > function requires that the caller provide external serialisation, via i_sem.
>
> O_APPEND|O_DIRECT writes could do that under XFS..

Sigh.

diff -puN include/linux/fs.h~i_size_write-check include/linux/fs.h
--- 25/include/linux/fs.h~i_size_write-check Fri Jan 30 15:09:47 2004
+++ 25-akpm/include/linux/fs.h Fri Jan 30 15:10:28 2004
@@ -464,9 +464,11 @@ static inline loff_t i_size_read(struct
#endif
}

+void i_size_write_check(struct inode *inode);

static inline void i_size_write(struct inode *inode, loff_t i_size)
{
+ i_size_write_check(inode);
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
write_seqcount_begin(&inode->i_size_seqcount);
inode->i_size = i_size;
diff -puN mm/filemap.c~i_size_write-check mm/filemap.c
--- 25/mm/filemap.c~i_size_write-check Fri Jan 30 15:10:23 2004
+++ 25-akpm/mm/filemap.c Fri Jan 30 15:11:41 2004
@@ -2010,3 +2010,18 @@ out:
}

EXPORT_SYMBOL_GPL(generic_file_direct_IO);
+
+void i_size_write_check(struct inode *inode)
+{
+ static int count = 0;
+
+ if (down_trylock(&inode->i_sem) == 0) {
+ if (count < 10) {
+ count++;
+ printk("i_size_write() called without i_sem\n");
+ dump_stack();
+ }
+ up(&inode->i_sem);
+ }
+}
+EXPORT_SYMBOL(i_size_write_check);

_