[PATCH v4 1/3] dax: masking off __GFP_FS in fs DAX handlers

[Dave Jiang <dave.jiang@intel.com>]

The caller into dax needs to clear __GFP_FS mask bit since it's
responsible for acquiring locks / transactions that blocks __GFP_FS
allocation.  The caller will restore the original mask when dax function
returns.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c          |    1 +
 fs/ext2/file.c    |    9 ++++++++-
 fs/ext4/file.c    |   10 +++++++++-
 fs/xfs/xfs_file.c |   14 +++++++++++++-
 4 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index d3fe880..6395bc6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1380,6 +1380,7 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 	vmf.pgoff = pgoff;
 	vmf.flags = flags;
 	vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+	vmf.gfp_mask &= ~__GFP_FS;
 
 	switch (iomap.type) {
 	case IOMAP_MAPPED:
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index b0f2415..8422d5f 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -92,16 +92,19 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	struct inode *inode = file_inode(vma->vm_file);
 	struct ext2_inode_info *ei = EXT2_I(inode);
 	int ret;
+	gfp_t old_gfp = vmf->gfp_mask;
 
 	if (vmf->flags & FAULT_FLAG_WRITE) {
 		sb_start_pagefault(inode->i_sb);
 		file_update_time(vma->vm_file);
 	}
+	vmf->gfp_mask &= ~__GFP_FS;
 	down_read(&ei->dax_sem);
 
 	ret = dax_iomap_fault(vma, vmf, &ext2_iomap_ops);
 
 	up_read(&ei->dax_sem);
+	vmf->gfp_mask = old_gfp;
 	if (vmf->flags & FAULT_FLAG_WRITE)
 		sb_end_pagefault(inode->i_sb);
 	return ret;
@@ -114,6 +117,7 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 	struct ext2_inode_info *ei = EXT2_I(inode);
 	loff_t size;
 	int ret;
+	gfp_t old_gfp = vmf->gfp_mask;
 
 	sb_start_pagefault(inode->i_sb);
 	file_update_time(vma->vm_file);
@@ -123,8 +127,11 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (vmf->pgoff >= size)
 		ret = VM_FAULT_SIGBUS;
-	else
+	else {
+		vmf->gfp_mask &= ~__GFP_FS;
 		ret = dax_pfn_mkwrite(vma, vmf);
+		vmf->gfp_mask = old_gfp;
+	}
 
 	up_read(&ei->dax_sem);
 	sb_end_pagefault(inode->i_sb);
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index d663d3d..a3f2bf0 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -261,14 +261,17 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	struct inode *inode = file_inode(vma->vm_file);
 	struct super_block *sb = inode->i_sb;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
+	gfp_t old_gfp = vmf->gfp_mask;
 
 	if (write) {
 		sb_start_pagefault(sb);
 		file_update_time(vma->vm_file);
 	}
+	vmf->gfp_mask &= ~__GFP_FS;
 	down_read(&EXT4_I(inode)->i_mmap_sem);
 	result = dax_iomap_fault(vma, vmf, &ext4_iomap_ops);
 	up_read(&EXT4_I(inode)->i_mmap_sem);
+	vmf->gfp_mask = old_gfp;
 	if (write)
 		sb_end_pagefault(sb);
 
@@ -320,8 +323,13 @@ static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
 	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (vmf->pgoff >= size)
 		ret = VM_FAULT_SIGBUS;
-	else
+	else {
+		gfp_t old_gfp = vmf->gfp_mask;
+
+		vmf->gfp_mask &= ~__GFP_FS;
 		ret = dax_pfn_mkwrite(vma, vmf);
+		vmf->gfp_mask = old_gfp;
+	}
 	up_read(&EXT4_I(inode)->i_mmap_sem);
 	sb_end_pagefault(sb);
 
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index d818c16..52202b4 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1474,7 +1474,11 @@ xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
+		gfp_t old_gfp = vmf->gfp_mask;
+
+		vmf->gfp_mask &= ~__GFP_FS;
 		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
+		vmf->gfp_mask = old_gfp;
 	} else {
 		ret = iomap_page_mkwrite(vma, vmf, &xfs_iomap_ops);
 		ret = block_page_mkwrite_return(ret);
@@ -1502,13 +1506,16 @@ xfs_filemap_fault(
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 	if (IS_DAX(inode)) {
+		gfp_t old_gfp = vmf->gfp_mask;
 		/*
 		 * we do not want to trigger unwritten extent conversion on read
 		 * faults - that is unnecessary overhead and would also require
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
+		vmf->gfp_mask &= ~__GFP_FS;
 		ret = dax_iomap_fault(vma, vmf, &xfs_iomap_ops);
+		vmf->gfp_mask = old_gfp;
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
@@ -1581,8 +1588,13 @@ xfs_filemap_pfn_mkwrite(
 	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (vmf->pgoff >= size)
 		ret = VM_FAULT_SIGBUS;
-	else if (IS_DAX(inode))
+	else if (IS_DAX(inode)) {
+		gfp_t old_gfp = vmf->gfp_mask;
+
+		vmf->gfp_mask &= ~__GFP_FS;
 		ret = dax_pfn_mkwrite(vma, vmf);
+		vmf->gfp_mask = old_gfp;
+	}
 	xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
 	sb_end_pagefault(inode->i_sb);
 	return ret;

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