[patch] fix file position for hugetlbfs-read-support

[patch] fix file position for hugetlbfs-read-support

[Ken Chen]

While working on a related area, I ran into a bug in hugetlbfs file
read support that is currently in -mm tree
(hugetlbfs-read-support.patch).

The problem is that hugetlb file position wasn't updated in
hugetlbfs_read(), so sys_read() will always read from same file
location.  A simple "cp" command that reads file until EOF will never
terminate.  Fix it by updating the ppos at the end of
hugetlbfs_read().

Signed-off-by: Ken Chen <kenchen@google.com>


diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 6dde2c3..8d9a631 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -228,9 +228,9 @@ hugetlbfs_read(struct file *filp
 	struct address_space *mapping = filp->f_mapping;
 	struct inode *inode = mapping->host;
 	unsigned long index = *ppos >> HPAGE_SHIFT;
+	unsigned long offset = *ppos & ~HPAGE_MASK;
 	unsigned long end_index;
 	loff_t isize;
-	unsigned long offset;
 	ssize_t retval = 0;

 	/* validate length */
@@ -241,7 +241,6 @@ hugetlbfs_read(struct file *filp
 	if (!isize)
 		goto out;

-	offset = *ppos & ~HPAGE_MASK;
 	end_index = (isize - 1) >> HPAGE_SHIFT;
 	for (;;) {
 		struct page *page;
@@ -290,6 +289,7 @@ hugetlbfs_read(struct file *filp
 		goto out;
 	}
 out:
+	*ppos = ((loff_t) index << HPAGE_SHIFT) + offset;
 	return retval;
 }

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Re: [patch] fix file position for hugetlbfs-read-support

[Badari Pulavarty]

On Tue, 2007-10-02 at 15:30 -0700, Ken Chen wrote:
> While working on a related area, I ran into a bug in hugetlbfs file
> read support that is currently in -mm tree
> (hugetlbfs-read-support.patch).
> 
> The problem is that hugetlb file position wasn't updated in
> hugetlbfs_read(), so sys_read() will always read from same file
> location.  A simple "cp" command that reads file until EOF will never
> terminate.  Fix it by updating the ppos at the end of
> hugetlbfs_read().
> 
> Signed-off-by: Ken Chen <kenchen@google.com>
> 

Acked-by: Badari Pulavarty <pbadari@us.ibm.com>

Thank you.

Thanks,
Badari

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