[RFC PATCH 5/5] btrfs: function to convert file offset to device offset
From: Goldwyn Rodrigues <hidden>
Date: 2021-10-22 20:15:46
Also in:
linux-fsdevel
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
From: Goldwyn Rodrigues <redacted> btrfs_file_to_device_offset() converts a file offset to device offset. It also calculates the last_index which represents the last page in the range which is within the extent. btrfs_file_to_device_offset() is only passed conditionally based on if BTRFS_SHAREDEXT is set in the mount flag. Signed-off-by: Goldwyn Rodrigues <redacted> --- fs/btrfs/file.c | 42 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 40 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index e171d822a05e..f0b97d020575 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c@@ -3643,18 +3643,56 @@ static ssize_t btrfs_direct_read(struct kiocb *iocb, struct iov_iter *to) return ret; } +static pgoff_t btrfs_file_offset_to_device(struct file *filp, loff_t pos, + size_t len, pgoff_t *last_index) +{ + struct extent_map *em; + struct btrfs_inode *inode = BTRFS_I(file_inode(filp)); + u64 device_offset; + u64 device_len; + + if (inode->flags & BTRFS_INODE_NODATACOW) + return 0; + + em = btrfs_get_extent(inode, NULL, 0, pos, len); + + device_offset = em->block_start; + if (device_offset == EXTENT_MAP_HOLE) { + free_extent_map(em); + return 0; + } + + /* Delalloc should be in file's pagecache */ + BUG_ON(device_offset == EXTENT_MAP_DELALLOC); + + device_offset = (device_offset + (pos - em->start)) >> PAGE_SHIFT; + device_len = (em->len - (pos - em->start)) >> PAGE_SHIFT; + *last_index = device_offset + device_len; + + free_extent_map(em); + + return device_offset; +} + static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) { ssize_t ret = 0; + struct inode *inode = file_inode(iocb->ki_filp); + struct btrfs_fs_info *fs_info; + file_offset_to_device_t file_offset_to_device = NULL; if (iocb->ki_flags & IOCB_DIRECT) { ret = btrfs_direct_read(iocb, to); if (ret < 0 || !iov_iter_count(to) || - iocb->ki_pos >= i_size_read(file_inode(iocb->ki_filp))) + iocb->ki_pos >= i_size_read(inode)) return ret; } - return filemap_read(iocb, to, ret, NULL); + fs_info = btrfs_sb(inode->i_sb); + if (btrfs_test_opt(fs_info, SHAREDEXT)) + file_offset_to_device = btrfs_file_offset_to_device; + + return filemap_read(iocb, to, ret, file_offset_to_device); } const struct file_operations btrfs_file_operations = {
--
2.33.1