[PATCH U-BOOT v3 25/30] fs: btrfs: Implement btrfs_file_read()
Marek Behún
marek.behun at nic.cz
Wed Jun 24 18:03:11 CEST 2020
From: Qu Wenruo <wqu at suse.com>
This version of btrfs_file_read() has the following new features:
- Tries all mirrors
- More handling on unaligned size
- Better compressed extent handling
The old implementation doesn't handle compressed extent with offset
properly: we need to read out the whole compressed extent, then
decompress the whole extent, and only then copy the requested part.
Signed-off-by: Qu Wenruo <wqu at suse.com>
Reviewed-by: Marek Behún <marek.behun at nic.cz>
---
fs/btrfs/btrfs.c | 48 +++++++++-------
fs/btrfs/btrfs.h | 2 +
fs/btrfs/inode.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 176 insertions(+), 20 deletions(-)
diff --git a/fs/btrfs/btrfs.c b/fs/btrfs/btrfs.c
index 7eb01c4ff9..ffd96427cc 100644
--- a/fs/btrfs/btrfs.c
+++ b/fs/btrfs/btrfs.c
@@ -253,37 +253,45 @@ out:
int btrfs_read(const char *file, void *buf, loff_t offset, loff_t len,
loff_t *actread)
{
- struct __btrfs_root root = btrfs_info.fs_root;
- struct btrfs_inode_item inode;
- u64 inr, rd;
+ struct btrfs_fs_info *fs_info = current_fs_info;
+ struct btrfs_root *root;
+ loff_t real_size;
+ u64 ino;
u8 type;
+ int ret;
- inr = __btrfs_lookup_path(&root, root.root_dirid, file, &type, &inode,
- 40);
-
- if (inr == -1ULL) {
- printf("Cannot lookup file %s\n", file);
- return -1;
+ ASSERT(fs_info);
+ ret = btrfs_lookup_path(fs_info->fs_root, BTRFS_FIRST_FREE_OBJECTID,
+ file, &root, &ino, &type, 40);
+ if (ret < 0) {
+ error("Cannot lookup file %s", file);
+ return ret;
}
if (type != BTRFS_FT_REG_FILE) {
- printf("Not a regular file: %s\n", file);
- return -1;
+ error("Not a regular file: %s", file);
+ return -EINVAL;
}
- if (!len)
- len = inode.size;
+ if (!len) {
+ ret = btrfs_size(file, &real_size);
+ if (ret < 0) {
+ error("Failed to get inode size: %s", file);
+ return ret;
+ }
+ len = real_size;
+ }
- if (len > inode.size - offset)
- len = inode.size - offset;
+ if (len > real_size - offset)
+ len = real_size - offset;
- rd = __btrfs_file_read(&root, inr, offset, len, buf);
- if (rd == -1ULL) {
- printf("An error occured while reading file %s\n", file);
- return -1;
+ ret = btrfs_file_read(root, ino, offset, len, buf);
+ if (ret < 0) {
+ error("An error occured while reading file %s", file);
+ return ret;
}
- *actread = rd;
+ *actread = len;
return 0;
}
diff --git a/fs/btrfs/btrfs.h b/fs/btrfs/btrfs.h
index 32ea2fc53a..268ca077d9 100644
--- a/fs/btrfs/btrfs.h
+++ b/fs/btrfs/btrfs.h
@@ -59,6 +59,8 @@ int btrfs_readlink(struct btrfs_root *root, u64 ino, char *target);
u64 __btrfs_lookup_path(struct __btrfs_root *, u64, const char *, u8 *,
struct btrfs_inode_item *, int);
u64 __btrfs_file_read(const struct __btrfs_root *, u64, u64, u64, char *);
+int btrfs_file_read(struct btrfs_root *root, u64 ino, u64 file_offset, u64 len,
+ char *dest);
/* subvolume.c */
u64 btrfs_get_default_subvol_objectid(void);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 11eb30c27a..0c2b2b5705 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -926,3 +926,149 @@ check_next:
*next_offset = key.offset;
return 1;
}
+
+static int read_and_truncate_page(struct btrfs_path *path,
+ struct btrfs_file_extent_item *fi,
+ int start, int len, char *dest)
+{
+ struct extent_buffer *leaf = path->nodes[0];
+ struct btrfs_fs_info *fs_info = leaf->fs_info;
+ u64 aligned_start = round_down(start, fs_info->sectorsize);
+ u8 extent_type;
+ char *buf;
+ int page_off = start - aligned_start;
+ int page_len = fs_info->sectorsize - page_off;
+ int ret;
+
+ ASSERT(start + len <= aligned_start + fs_info->sectorsize);
+ buf = malloc_cache_aligned(fs_info->sectorsize);
+ if (!buf)
+ return -ENOMEM;
+
+ extent_type = btrfs_file_extent_type(leaf, fi);
+ if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+ ret = btrfs_read_extent_inline(path, fi, buf);
+ memcpy(dest, buf + page_off, min(page_len, ret));
+ free(buf);
+ return len;
+ }
+
+ ret = btrfs_read_extent_reg(path, fi,
+ round_down(start, fs_info->sectorsize),
+ fs_info->sectorsize, buf);
+ if (ret < 0) {
+ free(buf);
+ return ret;
+ }
+ memcpy(dest, buf + page_off, page_len);
+ free(buf);
+ return len;
+}
+
+int btrfs_file_read(struct btrfs_root *root, u64 ino, u64 file_offset, u64 len,
+ char *dest)
+{
+ struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_file_extent_item *fi;
+ struct btrfs_path path;
+ struct btrfs_key key;
+ u64 aligned_start = round_down(file_offset, fs_info->sectorsize);
+ u64 aligned_end = round_down(file_offset + len, fs_info->sectorsize);
+ u64 next_offset;
+ u64 cur = aligned_start;
+ int ret = 0;
+
+ btrfs_init_path(&path);
+
+ /* Set the whole dest all zero, so we won't need to bother holes */
+ memset(dest, 0, len);
+
+ /* Read out the leading unaligned part */
+ if (aligned_start != file_offset) {
+ ret = lookup_data_extent(root, &path, ino, aligned_start,
+ &next_offset);
+ if (ret < 0)
+ goto out;
+ if (ret == 0) {
+ /* Read the unaligned part out*/
+ fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
+ struct btrfs_file_extent_item);
+ ret = read_and_truncate_page(&path, fi, file_offset,
+ round_up(file_offset, fs_info->sectorsize) -
+ file_offset, dest);
+ if (ret < 0)
+ goto out;
+ cur += fs_info->sectorsize;
+ } else {
+ /* The whole file is a hole */
+ if (!next_offset) {
+ memset(dest, 0, len);
+ return len;
+ }
+ cur = next_offset;
+ }
+ }
+
+ /* Read the aligned part */
+ while (cur < aligned_end) {
+ u64 extent_num_bytes;
+ u8 type;
+
+ btrfs_release_path(&path);
+ ret = lookup_data_extent(root, &path, ino, cur, &next_offset);
+ if (ret < 0)
+ goto out;
+ if (ret > 0) {
+ /* No next, direct exit */
+ if (!next_offset) {
+ ret = 0;
+ goto out;
+ }
+ }
+ fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
+ struct btrfs_file_extent_item);
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+ type = btrfs_file_extent_type(path.nodes[0], fi);
+ if (type == BTRFS_FILE_EXTENT_INLINE) {
+ ret = btrfs_read_extent_inline(&path, fi, dest);
+ goto out;
+ }
+ /* Skip holes, as we have zeroed the dest */
+ if (type == BTRFS_FILE_EXTENT_PREALLOC ||
+ btrfs_file_extent_disk_bytenr(path.nodes[0], fi) == 0) {
+ cur = key.offset + btrfs_file_extent_num_bytes(
+ path.nodes[0], fi);
+ continue;
+ }
+
+ /* Read the remaining part of the extent */
+ extent_num_bytes = btrfs_file_extent_num_bytes(path.nodes[0],
+ fi);
+ ret = btrfs_read_extent_reg(&path, fi, cur,
+ min(extent_num_bytes, aligned_end - cur),
+ dest + cur - file_offset);
+ if (ret < 0)
+ goto out;
+ cur += min(extent_num_bytes, aligned_end - cur);
+ }
+
+ /* Read the tailing unaligned part*/
+ if (file_offset + len != aligned_end) {
+ btrfs_release_path(&path);
+ ret = lookup_data_extent(root, &path, ino, aligned_end,
+ &next_offset);
+ /* <0 is error, >0 means no extent */
+ if (ret)
+ goto out;
+ fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
+ struct btrfs_file_extent_item);
+ ret = read_and_truncate_page(&path, fi, aligned_end,
+ file_offset + len - aligned_end,
+ dest + aligned_end - file_offset);
+ }
+out:
+ btrfs_release_path(&path);
+ if (ret < 0)
+ return ret;
+ return len;
+}
--
2.26.2
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