linux-kernel - [PATCH v2.1 08/14] fsdax: Output address in dax_iomap

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Date:   Tue, 7 Jun 2022 22:38:37 +0800
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-fsdevel@...r.kernel.org>, <akpm@...ux-foundation.org>
CC:     <djwong@...nel.org>, <dan.j.williams@...el.com>,
        <david@...morbit.com>, <hch@...radead.org>, <jane.chu@...cle.com>,
        <rgoldwyn@...e.de>, <viro@...iv.linux.org.uk>,
        <willy@...radead.org>, <naoya.horiguchi@....com>,
        <linmiaohe@...wei.com>, Christoph Hellwig <hch@....de>,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: [PATCH v2.1 08/14] fsdax: Output address in dax_iomap_pfn() and rename it

Add address output in dax_iomap_pfn() in order to perform a memcpy() in
CoW case.  Since this function both output address and pfn, rename it to
dax_iomap_direct_access().

Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

==
Hi Andrew,

As Dan mentioned[1], the rc should be initialized.  I fixed it and resend this patch.

[1] https://lore.kernel.org/linux-fsdevel/Yp8FUZnO64Qvyx5G@kili/

---
 fs/dax.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index b59b864017ad..7a8eb1e30a1b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1026,20 +1026,22 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 }
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 
-static int dax_iomap_pfn(const struct iomap *iomap, loff_t pos, size_t size,
-			 pfn_t *pfnp)
+static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
+		size_t size, void **kaddr, pfn_t *pfnp)
 {
 	pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
-	int id, rc;
+	int id, rc = 0;
 	long length;
 
 	id = dax_read_lock();
 	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
-				   DAX_ACCESS, NULL, pfnp);
+				   DAX_ACCESS, kaddr, pfnp);
 	if (length < 0) {
 		rc = length;
 		goto out;
 	}
+	if (!pfnp)
+		goto out_check_addr;
 	rc = -EINVAL;
 	if (PFN_PHYS(length) < size)
 		goto out;
@@ -1049,6 +1051,12 @@ static int dax_iomap_pfn(const struct iomap *iomap, loff_t pos, size_t size,
 	if (length > 1 && !pfn_t_devmap(*pfnp))
 		goto out;
 	rc = 0;
+
+out_check_addr:
+	if (!kaddr)
+		goto out;
+	if (!*kaddr)
+		rc = -EFAULT;
 out:
 	dax_read_unlock(id);
 	return rc;
@@ -1456,7 +1464,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 		return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
 	}
 
-	err = dax_iomap_pfn(&iter->iomap, pos, size, &pfn);
+	err = dax_iomap_direct_access(&iter->iomap, pos, size, NULL, &pfn);
 	if (err)
 		return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
 
-- 
2.36.1