diff mbox

[10/42] btrfs: use bio fields for op and flags

Message ID 1460576188-5751-11-git-send-email-mchristi@redhat.com (mailing list archive)
State Superseded
Headers show

Commit Message

Mike Christie April 13, 2016, 7:35 p.m. UTC 
From: Mike Christie <mchristi@redhat.com>

The bio bi_op and bi_rw is now setup, so there is no need
to pass around the rq_flag_bits bits too. btrfs users should should
access the bio.

v2:

1. Fix merge_bio issue where instead of removing rw/op argument
I passed it in again to the merge_bio related functions.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/compression.c | 13 ++++++-------
 fs/btrfs/ctree.h       |  2 +-
 fs/btrfs/disk-io.c     | 30 ++++++++++++------------------
 fs/btrfs/disk-io.h     |  2 +-
 fs/btrfs/extent_io.c   | 12 +++++-------
 fs/btrfs/extent_io.h   |  8 ++++----
 fs/btrfs/inode.c       | 44 ++++++++++++++++++++------------------------
 fs/btrfs/volumes.c     |  6 +++---
 fs/btrfs/volumes.h     |  2 +-
 9 files changed, 53 insertions(+), 66 deletions(-)
diff mbox

Patch

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 334a00c..356ac36 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -374,7 +374,7 @@  int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		page = compressed_pages[pg_index];
 		page->mapping = inode->i_mapping;
 		if (bio->bi_iter.bi_size)
-			ret = io_tree->ops->merge_bio_hook(WRITE, page, 0,
+			ret = io_tree->ops->merge_bio_hook(page, 0,
 							   PAGE_SIZE,
 							   bio, 0);
 		else
@@ -402,7 +402,7 @@  int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 				BUG_ON(ret); /* -ENOMEM */
 			}
 
-			ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
+			ret = btrfs_map_bio(root, bio, 0, 1);
 			BUG_ON(ret); /* -ENOMEM */
 
 			bio_put(bio);
@@ -433,7 +433,7 @@  int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		BUG_ON(ret); /* -ENOMEM */
 	}
 
-	ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
+	ret = btrfs_map_bio(root, bio, 0, 1);
 	BUG_ON(ret); /* -ENOMEM */
 
 	bio_put(bio);
@@ -659,7 +659,7 @@  int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		page->index = em_start >> PAGE_SHIFT;
 
 		if (comp_bio->bi_iter.bi_size)
-			ret = tree->ops->merge_bio_hook(READ, page, 0,
+			ret = tree->ops->merge_bio_hook(page, 0,
 							PAGE_SIZE,
 							comp_bio, 0);
 		else
@@ -690,8 +690,7 @@  int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
 					     root->sectorsize);
 
-			ret = btrfs_map_bio(root, READ, comp_bio,
-					    mirror_num, 0);
+			ret = btrfs_map_bio(root, comp_bio, mirror_num, 0);
 			if (ret) {
 				bio->bi_error = ret;
 				bio_endio(comp_bio);
@@ -721,7 +720,7 @@  int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		BUG_ON(ret); /* -ENOMEM */
 	}
 
-	ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
+	ret = btrfs_map_bio(root, comp_bio, mirror_num, 0);
 	if (ret) {
 		bio->bi_error = ret;
 		bio_endio(comp_bio);
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a0c6aca..4e50f59 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -4087,7 +4087,7 @@  int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
 			     struct btrfs_root *parent_root,
 			     u64 new_dirid);
-int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
+int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags);
 int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 932268b..bea6df6 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -124,7 +124,6 @@  struct async_submit_bio {
 	struct list_head list;
 	extent_submit_bio_hook_t *submit_bio_start;
 	extent_submit_bio_hook_t *submit_bio_done;
-	int rw;
 	int mirror_num;
 	unsigned long bio_flags;
 	/*
@@ -797,7 +796,7 @@  static void run_one_async_start(struct btrfs_work *work)
 	int ret;
 
 	async = container_of(work, struct  async_submit_bio, work);
-	ret = async->submit_bio_start(async->inode, async->rw, async->bio,
+	ret = async->submit_bio_start(async->inode, async->bio,
 				      async->mirror_num, async->bio_flags,
 				      async->bio_offset);
 	if (ret)
@@ -830,9 +829,8 @@  static void run_one_async_done(struct btrfs_work *work)
 		return;
 	}
 
-	async->submit_bio_done(async->inode, async->rw, async->bio,
-			       async->mirror_num, async->bio_flags,
-			       async->bio_offset);
+	async->submit_bio_done(async->inode, async->bio, async->mirror_num,
+			       async->bio_flags, async->bio_offset);
 }
 
 static void run_one_async_free(struct btrfs_work *work)
@@ -844,7 +842,7 @@  static void run_one_async_free(struct btrfs_work *work)
 }
 
 int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
-			int rw, struct bio *bio, int mirror_num,
+			struct bio *bio, int mirror_num,
 			unsigned long bio_flags,
 			u64 bio_offset,
 			extent_submit_bio_hook_t *submit_bio_start,
@@ -857,7 +855,6 @@  int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
 		return -ENOMEM;
 
 	async->inode = inode;
-	async->rw = rw;
 	async->bio = bio;
 	async->mirror_num = mirror_num;
 	async->submit_bio_start = submit_bio_start;
@@ -903,9 +900,8 @@  static int btree_csum_one_bio(struct bio *bio)
 	return ret;
 }
 
-static int __btree_submit_bio_start(struct inode *inode, int rw,
-				    struct bio *bio, int mirror_num,
-				    unsigned long bio_flags,
+static int __btree_submit_bio_start(struct inode *inode, struct bio *bio,
+				    int mirror_num, unsigned long bio_flags,
 				    u64 bio_offset)
 {
 	/*
@@ -915,7 +911,7 @@  static int __btree_submit_bio_start(struct inode *inode, int rw,
 	return btree_csum_one_bio(bio);
 }
 
-static int __btree_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
+static int __btree_submit_bio_done(struct inode *inode, struct bio *bio,
 				 int mirror_num, unsigned long bio_flags,
 				 u64 bio_offset)
 {
@@ -925,7 +921,7 @@  static int __btree_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
 	 * when we're called for a write, we're already in the async
 	 * submission context.  Just jump into btrfs_map_bio
 	 */
-	ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 1);
+	ret = btrfs_map_bio(BTRFS_I(inode)->root, bio, mirror_num, 1);
 	if (ret) {
 		bio->bi_error = ret;
 		bio_endio(bio);
@@ -944,7 +940,7 @@  static int check_async_write(struct inode *inode, unsigned long bio_flags)
 	return 1;
 }
 
-static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
+static int btree_submit_bio_hook(struct inode *inode, struct bio *bio,
 				 int mirror_num, unsigned long bio_flags,
 				 u64 bio_offset)
 {
@@ -960,21 +956,19 @@  static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 					  bio, BTRFS_WQ_ENDIO_METADATA);
 		if (ret)
 			goto out_w_error;
-		ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
-				    mirror_num, 0);
+		ret = btrfs_map_bio(BTRFS_I(inode)->root, bio, mirror_num, 0);
 	} else if (!async) {
 		ret = btree_csum_one_bio(bio);
 		if (ret)
 			goto out_w_error;
-		ret = btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
-				    mirror_num, 0);
+		ret = btrfs_map_bio(BTRFS_I(inode)->root, bio, mirror_num, 0);
 	} else {
 		/*
 		 * kthread helpers are used to submit writes so that
 		 * checksumming can happen in parallel across all CPUs
 		 */
 		ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
-					  inode, rw, bio, mirror_num, 0,
+					  inode, bio, mirror_num, 0,
 					  bio_offset,
 					  __btree_submit_bio_start,
 					  __btree_submit_bio_done);
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 8e79d00..73c21a2 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -122,7 +122,7 @@  void btrfs_csum_final(u32 crc, char *result);
 int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
 			enum btrfs_wq_endio_type metadata);
 int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
-			int rw, struct bio *bio, int mirror_num,
+			struct bio *bio, int mirror_num,
 			unsigned long bio_flags, u64 bio_offset,
 			extent_submit_bio_hook_t *submit_bio_start,
 			extent_submit_bio_hook_t *submit_bio_done);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 45fa3be..3bac80d 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2409,8 +2409,7 @@  static int bio_readpage_error(struct bio *failed_bio, u64 phy_offset,
 	pr_debug("Repair Read Error: submitting new read[%#x] to this_mirror=%d, in_validation=%d\n",
 		 read_mode, failrec->this_mirror, failrec->in_validation);
 
-	ret = tree->ops->submit_bio_hook(inode, read_mode, bio,
-					 failrec->this_mirror,
+	ret = tree->ops->submit_bio_hook(inode, bio, failrec->this_mirror,
 					 failrec->bio_flags, 0);
 	if (ret) {
 		free_io_failure(inode, failrec);
@@ -2731,9 +2730,8 @@  static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
 	bio_get(bio);
 
 	if (tree->ops && tree->ops->submit_bio_hook)
-		ret = tree->ops->submit_bio_hook(page->mapping->host,
-						 bio->bi_rw, bio, mirror_num,
-						 bio_flags, start);
+		ret = tree->ops->submit_bio_hook(page->mapping->host, bio,
+					   mirror_num, bio_flags, start);
 	else
 		btrfsic_submit_bio(bio);
 
@@ -2747,8 +2745,8 @@  static int merge_bio(struct extent_io_tree *tree, struct page *page,
 {
 	int ret = 0;
 	if (tree->ops && tree->ops->merge_bio_hook)
-		ret = tree->ops->merge_bio_hook(bio->bi_op, page, offset, size,
-						bio, bio_flags);
+		ret = tree->ops->merge_bio_hook(page, offset, size, bio,
+						bio_flags);
 	BUG_ON(ret < 0);
 	return ret;
 
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index b5e0ade..f8db2fd 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -63,9 +63,9 @@  struct btrfs_root;
 struct btrfs_io_bio;
 struct io_failure_record;
 
-typedef	int (extent_submit_bio_hook_t)(struct inode *inode, int rw,
-				       struct bio *bio, int mirror_num,
-				       unsigned long bio_flags, u64 bio_offset);
+typedef	int (extent_submit_bio_hook_t)(struct inode *inode, struct bio *bio,
+				       int mirror_num, unsigned long bio_flags,
+				       u64 bio_offset);
 struct extent_io_ops {
 	int (*fill_delalloc)(struct inode *inode, struct page *locked_page,
 			     u64 start, u64 end, int *page_started,
@@ -73,7 +73,7 @@  struct extent_io_ops {
 	int (*writepage_start_hook)(struct page *page, u64 start, u64 end);
 	int (*writepage_io_hook)(struct page *page, u64 start, u64 end);
 	extent_submit_bio_hook_t *submit_bio_hook;
-	int (*merge_bio_hook)(int rw, struct page *page, unsigned long offset,
+	int (*merge_bio_hook)(struct page *page, unsigned long offset,
 			      size_t size, struct bio *bio,
 			      unsigned long bio_flags);
 	int (*readpage_io_failed_hook)(struct page *page, int failed_mirror);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c2dc75b..bd214ab 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1807,7 +1807,7 @@  static void btrfs_clear_bit_hook(struct inode *inode,
  * extent_io.c merge_bio_hook, this must check the chunk tree to make sure
  * we don't create bios that span stripes or chunks
  */
-int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
+int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags)
 {
@@ -1822,7 +1822,7 @@  int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
 
 	length = bio->bi_iter.bi_size;
 	map_length = length;
-	ret = btrfs_map_block(root->fs_info, rw, logical,
+	ret = btrfs_map_block(root->fs_info, bio->bi_op, logical,
 			      &map_length, NULL, 0);
 	/* Will always return 0 with map_multi == NULL */
 	BUG_ON(ret < 0);
@@ -1839,9 +1839,8 @@  int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
  * At IO completion time the cums attached on the ordered extent record
  * are inserted into the btree
  */
-static int __btrfs_submit_bio_start(struct inode *inode, int rw,
-				    struct bio *bio, int mirror_num,
-				    unsigned long bio_flags,
+static int __btrfs_submit_bio_start(struct inode *inode, struct bio *bio,
+				    int mirror_num, unsigned long bio_flags,
 				    u64 bio_offset)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
@@ -1860,14 +1859,14 @@  static int __btrfs_submit_bio_start(struct inode *inode, int rw,
  * At IO completion time the cums attached on the ordered extent record
  * are inserted into the btree
  */
-static int __btrfs_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
+static int __btrfs_submit_bio_done(struct inode *inode, struct bio *bio,
 			  int mirror_num, unsigned long bio_flags,
 			  u64 bio_offset)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;
 
-	ret = btrfs_map_bio(root, rw, bio, mirror_num, 1);
+	ret = btrfs_map_bio(root, bio, mirror_num, 1);
 	if (ret) {
 		bio->bi_error = ret;
 		bio_endio(bio);
@@ -1879,7 +1878,7 @@  static int __btrfs_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
  * extent_io.c submission hook. This does the right thing for csum calculation
  * on write, or reading the csums from the tree before a read
  */
-static int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
+static int btrfs_submit_bio_hook(struct inode *inode, struct bio *bio,
 			  int mirror_num, unsigned long bio_flags,
 			  u64 bio_offset)
 {
@@ -1916,7 +1915,7 @@  static int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 			goto mapit;
 		/* we're doing a write, do the async checksumming */
 		ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
-				   inode, rw, bio, mirror_num,
+				   inode, bio, mirror_num,
 				   bio_flags, bio_offset,
 				   __btrfs_submit_bio_start,
 				   __btrfs_submit_bio_done);
@@ -1928,7 +1927,7 @@  static int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 	}
 
 mapit:
-	ret = btrfs_map_bio(root, rw, bio, mirror_num, 0);
+	ret = btrfs_map_bio(root, bio, mirror_num, 0);
 
 out:
 	if (ret < 0) {
@@ -7746,7 +7745,7 @@  err:
 }
 
 static inline int submit_dio_repair_bio(struct inode *inode, struct bio *bio,
-					int rw, int mirror_num)
+					int mirror_num)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;
@@ -7760,7 +7759,7 @@  static inline int submit_dio_repair_bio(struct inode *inode, struct bio *bio,
 	if (ret)
 		goto err;
 
-	ret = btrfs_map_bio(root, rw, bio, mirror_num, 0);
+	ret = btrfs_map_bio(root, bio, mirror_num, 0);
 err:
 	bio_put(bio);
 	return ret;
@@ -7846,8 +7845,7 @@  static int dio_read_error(struct inode *inode, struct bio *failed_bio,
 		    "Repair DIO Read Error: submitting new dio read[%#x] to this_mirror=%d, in_validation=%d\n",
 		    read_mode, failrec->this_mirror, failrec->in_validation);
 
-	ret = submit_dio_repair_bio(inode, bio, read_mode,
-				    failrec->this_mirror);
+	ret = submit_dio_repair_bio(inode, bio, failrec->this_mirror);
 	if (ret) {
 		free_io_failure(inode, failrec);
 		bio_put(bio);
@@ -8137,7 +8135,7 @@  static void btrfs_endio_direct_write(struct bio *bio)
 	bio_put(bio);
 }
 
-static int __btrfs_submit_bio_start_direct_io(struct inode *inode, int rw,
+static int __btrfs_submit_bio_start_direct_io(struct inode *inode,
 				    struct bio *bio, int mirror_num,
 				    unsigned long bio_flags, u64 offset)
 {
@@ -8230,7 +8228,7 @@  static inline int btrfs_lookup_and_bind_dio_csum(struct btrfs_root *root,
 }
 
 static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
-					 int rw, u64 file_offset, int skip_sum,
+					 u64 file_offset, int skip_sum,
 					 int async_submit)
 {
 	struct btrfs_dio_private *dip = bio->bi_private;
@@ -8255,8 +8253,7 @@  static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
 
 	if (write && async_submit) {
 		ret = btrfs_wq_submit_bio(root->fs_info,
-				   inode, rw, bio, 0, 0,
-				   file_offset,
+				   inode, bio, 0, 0, file_offset,
 				   __btrfs_submit_bio_start_direct_io,
 				   __btrfs_submit_bio_done);
 		goto err;
@@ -8275,13 +8272,13 @@  static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
 			goto err;
 	}
 map:
-	ret = btrfs_map_bio(root, rw, bio, 0, async_submit);
+	ret = btrfs_map_bio(root, bio, 0, async_submit);
 err:
 	bio_put(bio);
 	return ret;
 }
 
-static int btrfs_submit_direct_hook(int rw, struct btrfs_dio_private *dip,
+static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip,
 				    int skip_sum)
 {
 	struct inode *inode = dip->inode;
@@ -8342,7 +8339,7 @@  next_block:
 			 * before we're done setting it up
 			 */
 			atomic_inc(&dip->pending_bios);
-			ret = __btrfs_submit_dio_bio(bio, inode, rw,
+			ret = __btrfs_submit_dio_bio(bio, inode,
 						     file_offset, skip_sum,
 						     async_submit);
 			if (ret) {
@@ -8387,7 +8384,7 @@  next_block:
 	}
 
 submit:
-	ret = __btrfs_submit_dio_bio(bio, inode, rw, file_offset, skip_sum,
+	ret = __btrfs_submit_dio_bio(bio, inode, file_offset, skip_sum,
 				     async_submit);
 	if (!ret)
 		return 0;
@@ -8465,8 +8462,7 @@  static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 			dio_data->unsubmitted_oe_range_end;
 	}
 
-	ret = btrfs_submit_direct_hook(dio_bio->bi_op | dio_bio->bi_rw, dip,
-				       skip_sum);
+	ret = btrfs_submit_direct_hook(dip, skip_sum);
 	if (!ret)
 		return;
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index dc56558..2100514 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5995,7 +5995,7 @@  static noinline void btrfs_schedule_bio(struct btrfs_root *root,
 
 static void submit_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
 			      struct bio *bio, u64 physical, int dev_nr,
-			      int rw, int async)
+			      int async)
 {
 	struct btrfs_device *dev = bbio->stripes[dev_nr].dev;
 
@@ -6040,7 +6040,7 @@  static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
 	}
 }
 
-int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
+int btrfs_map_bio(struct btrfs_root *root, struct bio *bio,
 		  int mirror_num, int async_submit)
 {
 	struct btrfs_device *dev;
@@ -6107,7 +6107,7 @@  int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
 			bio = first_bio;
 
 		submit_stripe_bio(root, bbio, bio,
-				  bbio->stripes[dev_nr].physical, dev_nr, rw,
+				  bbio->stripes[dev_nr].physical, dev_nr,
 				  async_submit);
 	}
 	btrfs_bio_counter_dec(root->fs_info);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index c64229e..372974d0 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -437,7 +437,7 @@  int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *extent_root, u64 type);
 void btrfs_mapping_init(struct btrfs_mapping_tree *tree);
 void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree);
-int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
+int btrfs_map_bio(struct btrfs_root *root, struct bio *bio,
 		  int mirror_num, int async_submit);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);