linux-kernel - [PATCH 02/18] orangefs: implement vm

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Date:   Tue, 12 Dec 2017 13:34:08 -0500
From:   Martin Brandenburg <martin@...ibond.com>
To:     hubcap@...ibond.com, devel@...ts.orangefs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Martin Brandenburg <martin@...ibond.com>
Subject: [PATCH 02/18] orangefs: implement vm_ops->fault

From: Martin Brandenburg <martin@...ibond.com>

Must retrieve size before running filemap_fault so the kernel has
an up-to-date size.

This should have been caught by xfstests generic/246, but it was masked
by orangefs_new_inode, which set i_size to PAGE_SIZE.  When nothing
caused a getattr prior to a pagefault, i_size was still PAGE_SIZE.
Since xfstests only read 10 bytes, it did not catch this bug.

When orangefs_new_inode was modified to perform a getattr instead,
i_size was set to zero, as it was a newly created file.  Then
orangefs_file_write_iter did NOT set i_size, instead prefering to
invalidate the attribute cache and letting the next caller retrieve
i_size.  But the fault handler did not know it was supposed to retrieve
i_size.  So during xfstests, i_size was still zero, and filemap_fault
returned VM_FAULT_SIGBUS.

Fixes xfstests generic/080, generic/141, generic/215, generic/247,
generic/248, generic/437, and generic/452.

Signed-off-by: Martin Brandenburg <martin@...ibond.com>
---
 fs/orangefs/file.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/fs/orangefs/file.c b/fs/orangefs/file.c
index 44879b1ff33e..70909ee27323 100644
--- a/fs/orangefs/file.c
+++ b/fs/orangefs/file.c
@@ -531,6 +531,28 @@ static long orangefs_ioctl(struct file *file, unsigned int cmd, unsigned long ar
 	return ret;
 }

+static int orangefs_fault(struct vm_fault *vmf)
+{
+	struct file *file = vmf->vma->vm_file;
+	int rc;
+	rc = orangefs_inode_getattr(file->f_mapping->host, 0, 1,
+	    STATX_SIZE);
+	if (rc == -ESTALE)
+		rc = -EIO;
+	if (rc) {
+		gossip_err("%s: orangefs_inode_getattr failed, "
+		    "rc:%d:.\n", __func__, rc);
+		return rc;
+	}
+	return filemap_fault(vmf);
+}
+
+const struct vm_operations_struct orangefs_file_vm_ops = {
+	.fault = orangefs_fault,
+	.map_pages = filemap_map_pages,
+	.page_mkwrite = filemap_page_mkwrite,
+};
+
 /*
  * Memory map a region of a file.
  */
@@ -542,12 +564,16 @@ static int orangefs_file_mmap(struct file *file, struct vm_area_struct *vma)
 			(char *)file->f_path.dentry->d_name.name :
 			(char *)"Unknown"));

+	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+		return -EINVAL;
+
 	/* set the sequential readahead hint */
 	vma->vm_flags |= VM_SEQ_READ;
 	vma->vm_flags &= ~VM_RAND_READ;

-	/* Use readonly mmap since we cannot support writable maps. */
-	return generic_file_readonly_mmap(file, vma);
+	file_accessed(file);
+	vma->vm_ops = &orangefs_file_vm_ops;
+	return 0;
 }

 #define mapping_nrpages(idata) ((idata)->nrpages)
-- 
2.15.1