btrfs: Factor out write portion of btrfs_get_blocks_direct

Now that the read side is extracted into its own function, do the same
to the write side. This leaves btrfs_get_blocks_direct_write with the
sole purpose of handling common locking required. Also flip the
condition in btrfs_get_blocks_direct_write so that the write case
comes first and we check for if (Create) rather than if (!create). This
is purely subjective but I believe makes reading a bit more "linear".
No functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 108 insertions, 99 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4f8fb1130cf3..880431ae5e59 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7561,6 +7561,104 @@ static int btrfs_get_blocks_direct_read(struct extent_map *em,
         return 0;
 }
 
+static int btrfs_get_blocks_direct_write(struct extent_map **map,
+                                         struct buffer_head *bh_result,
+                                         struct inode *inode,
+                                         struct btrfs_dio_data *dio_data,
+                                         u64 start, u64 len)
+{
+        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+        struct extent_map *em = *map;
+        int ret = 0;
+
+        /*
+         * We don't allocate a new extent in the following cases
+         *
+         * 1) The inode is marked as NODATACOW. In this case we'll just use the
+         * existing extent.
+         * 2) The extent is marked as PREALLOC. We're good to go here and can
+         * just use the extent.
+         *
+         */
+        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
+            ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
+             em->block_start != EXTENT_MAP_HOLE)) {
+                int type;
+                u64 block_start, orig_start, orig_block_len, ram_bytes;
+
+                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+                        type = BTRFS_ORDERED_PREALLOC;
+                else
+                        type = BTRFS_ORDERED_NOCOW;
+                len = min(len, em->len - (start - em->start));
+                block_start = em->block_start + (start - em->start);
+
+                if (can_nocow_extent(inode, start, &len, &orig_start,
+                                     &orig_block_len, &ram_bytes) == 1 &&
+                    btrfs_inc_nocow_writers(fs_info, block_start)) {
+                        struct extent_map *em2;
+
+                        em2 = btrfs_create_dio_extent(inode, start, len,
+                                                      orig_start, block_start,
+                                                      len, orig_block_len,
+                                                      ram_bytes, type);
+                        btrfs_dec_nocow_writers(fs_info, block_start);
+                        if (type == BTRFS_ORDERED_PREALLOC) {
+                                free_extent_map(em);
+                                *map = em = em2;
+                        }
+
+                        if (em2 && IS_ERR(em2)) {
+                                ret = PTR_ERR(em2);
+                                goto out;
+                        }
+                        /*
+                         * For inode marked NODATACOW or extent marked PREALLOC,
+                         * use the existing or preallocated extent, so does not
+                         * need to adjust btrfs_space_info's bytes_may_use.
+                         */
+                        btrfs_free_reserved_data_space_noquota(inode, start,
+                                                               len);
+                        goto skip_cow;
+                }
+        }
+
+        /* this will cow the extent */
+        len = bh_result->b_size;
+        free_extent_map(em);
+        *map = em = btrfs_new_extent_direct(inode, start, len);
+        if (IS_ERR(em)) {
+                ret = PTR_ERR(em);
+                goto out;
+        }
+
+        len = min(len, em->len - (start - em->start));
+
+skip_cow:
+        bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
+                inode->i_blkbits;
+        bh_result->b_size = len;
+        bh_result->b_bdev = em->bdev;
+        set_buffer_mapped(bh_result);
+
+        if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+                set_buffer_new(bh_result);
+
+        /*
+         * Need to update the i_size under the extent lock so buffered
+         * readers will get the updated i_size when we unlock.
+         */
+        if (!dio_data->overwrite && start + len > i_size_read(inode))
+                i_size_write(inode, start + len);
+
+        WARN_ON(dio_data->reserve < len);
+        dio_data->reserve -= len;
+        dio_data->unsubmitted_oe_range_end = start + len;
+        current->journal_info = dio_data;
+out:
+        return ret;
+}
+
 static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                                    struct buffer_head *bh_result, int create)
 {
@@ -7629,7 +7727,16 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                 goto unlock_err;
         }
 
-        if (!create) {
+        if (create) {
+                ret = btrfs_get_blocks_direct_write(&em, bh_result, inode,
+                                                    dio_data, start, len);
+                if (ret < 0)
+                        goto unlock_err;
+
+                /* clear and unlock the entire range */
+                clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+                                 unlock_bits, 1, 0, &cached_state);
+        } else {
                 ret = btrfs_get_blocks_direct_read(em, bh_result, inode,
                                                    start, len);
                 /* Can be negative only if we read from a hole */
@@ -7650,106 +7757,8 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                 } else {
                         free_extent_state(cached_state);
                 }
-                free_extent_map(em);
-                return 0;
         }
 
-        /*
-         * We don't allocate a new extent in the following cases
-         *
-         * 1) The inode is marked as NODATACOW.  In this case we'll just use the
-         * existing extent.
-         * 2) The extent is marked as PREALLOC.  We're good to go here and can
-         * just use the extent.
-         *
-         */
-        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
-            ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
-             em->block_start != EXTENT_MAP_HOLE)) {
-                int type;
-                u64 block_start, orig_start, orig_block_len, ram_bytes;
-
-                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
-                        type = BTRFS_ORDERED_PREALLOC;
-                else
-                        type = BTRFS_ORDERED_NOCOW;
-                len = min(len, em->len - (start - em->start));
-                block_start = em->block_start + (start - em->start);
-
-                if (can_nocow_extent(inode, start, &len, &orig_start,
-                                     &orig_block_len, &ram_bytes) == 1 &&
-                    btrfs_inc_nocow_writers(fs_info, block_start)) {
-                        struct extent_map *em2;
-
-                        em2 = btrfs_create_dio_extent(inode, start, len,
-                                                      orig_start, block_start,
-                                                      len, orig_block_len,
-                                                      ram_bytes, type);
-                        btrfs_dec_nocow_writers(fs_info, block_start);
-                        if (type == BTRFS_ORDERED_PREALLOC) {
-                                free_extent_map(em);
-                                em = em2;
-                        }
-                        if (em2 && IS_ERR(em2)) {
-                                ret = PTR_ERR(em2);
-                                goto unlock_err;
-                        }
-                        /*
-                         * For inode marked NODATACOW or extent marked PREALLOC,
-                         * use the existing or preallocated extent, so does not
-                         * need to adjust btrfs_space_info's bytes_may_use.
-                         */
-                        btrfs_free_reserved_data_space_noquota(inode,
-                                        start, len);
-                        goto unlock;
-                }
-        }
-
-        /*
-         * this will cow the extent, reset the len in case we changed
-         * it above
-         */
-        len = bh_result->b_size;
-        free_extent_map(em);
-        em = btrfs_new_extent_direct(inode, start, len);
-        if (IS_ERR(em)) {
-                ret = PTR_ERR(em);
-                goto unlock_err;
-        }
-        len = min(len, em->len - (start - em->start));
-unlock:
-        bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
-                inode->i_blkbits;
-        bh_result->b_size = len;
-        bh_result->b_bdev = em->bdev;
-        set_buffer_mapped(bh_result);
-        if (create) {
-                if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
-                        set_buffer_new(bh_result);
-
-                /*
-                 * Need to update the i_size under the extent lock so buffered
-                 * readers will get the updated i_size when we unlock.
-                 */
-                if (!dio_data->overwrite && start + len > i_size_read(inode))
-                        i_size_write(inode, start + len);
-
-                WARN_ON(dio_data->reserve < len);
-                dio_data->reserve -= len;
-                dio_data->unsubmitted_oe_range_end = start + len;
-                current->journal_info = dio_data;
-        }
-
-        /*
-         * In the case of write we need to clear and unlock the entire range,
-         * in the case of read we need to unlock only the end area that we
-         * aren't using if there is any left over space.
-         */
-        if (lockstart < lockend) {
-                clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
-                                 lockend, unlock_bits, 1, 0,
-                                 &cached_state);
-        }
         free_extent_map(em);
 
         return 0;