Btrfs: Cleanup and comment ordered-data.c
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index b739e3a..230fd3c 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -136,6 +136,19 @@
return ret;
}
+/* allocate and add a new ordered_extent into the per-inode tree.
+ * file_offset is the logical offset in the file
+ *
+ * start is the disk block number of an extent already reserved in the
+ * extent allocation tree
+ *
+ * len is the length of the extent
+ *
+ * This also sets the EXTENT_ORDERED bit on the range in the inode.
+ *
+ * The tree is given a single reference on the ordered extent that was
+ * inserted.
+ */
int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
u64 start, u64 len)
{
@@ -152,7 +165,6 @@
entry->file_offset = file_offset;
entry->start = start;
entry->len = len;
- entry->inode = inode;
/* one ref for the tree */
atomic_set(&entry->refs, 1);
init_waitqueue_head(&entry->wait);
@@ -167,12 +179,15 @@
set_extent_ordered(&BTRFS_I(inode)->io_tree, file_offset,
entry_end(entry) - 1, GFP_NOFS);
- set_bit(BTRFS_ORDERED_START, &entry->flags);
mutex_unlock(&tree->mutex);
BUG_ON(node);
return 0;
}
+/*
+ * Add a struct btrfs_ordered_sum into the list of checksums to be inserted
+ * when an ordered extent is finished.
+ */
int btrfs_add_ordered_sum(struct inode *inode, struct btrfs_ordered_sum *sum)
{
struct btrfs_ordered_inode_tree *tree;
@@ -182,29 +197,25 @@
tree = &BTRFS_I(inode)->ordered_tree;
mutex_lock(&tree->mutex);
node = tree_search(tree, sum->file_offset);
- if (!node) {
-search_fail:
-printk("add ordered sum failed to find a node for inode %lu offset %Lu\n", inode->i_ino, sum->file_offset);
- node = rb_first(&tree->tree);
- while(node) {
- entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
- printk("entry %Lu %Lu %Lu\n", entry->file_offset, entry->file_offset + entry->len, entry->start);
- node = rb_next(node);
- }
- BUG();
- }
BUG_ON(!node);
entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
- if (!offset_in_entry(entry, sum->file_offset)) {
- goto search_fail;
- }
+ BUG_ON(!offset_in_entry(entry, sum->file_offset));
list_add_tail(&sum->list, &entry->list);
mutex_unlock(&tree->mutex);
return 0;
}
+/*
+ * this is used to account for finished IO across a given range
+ * of the file. The IO should not span ordered extents. If
+ * a given ordered_extent is completely done, 1 is returned, otherwise
+ * 0.
+ *
+ * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
+ * to make sure this function only returns 1 once for a given ordered extent.
+ */
int btrfs_dec_test_ordered_pending(struct inode *inode,
u64 file_offset, u64 io_size)
{
@@ -233,9 +244,6 @@
ret = test_range_bit(io_tree, entry->file_offset,
entry->file_offset + entry->len - 1,
EXTENT_ORDERED, 0);
- if (!test_bit(BTRFS_ORDERED_START, &entry->flags)) {
-printk("inode %lu not ready yet for extent %Lu %Lu\n", inode->i_ino, entry->file_offset, entry_end(entry));
- }
if (ret == 0)
ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
out:
@@ -243,6 +251,10 @@
return ret == 0;
}
+/*
+ * used to drop a reference on an ordered extent. This will free
+ * the extent if the last reference is dropped
+ */
int btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
{
struct list_head *cur;
@@ -260,6 +272,10 @@
return 0;
}
+/*
+ * remove an ordered extent from the tree. No references are dropped
+ * but, anyone waiting on this extent is woken up.
+ */
int btrfs_remove_ordered_extent(struct inode *inode,
struct btrfs_ordered_extent *entry)
{
@@ -277,27 +293,25 @@
return 0;
}
-void btrfs_wait_ordered_extent(struct inode *inode,
- struct btrfs_ordered_extent *entry)
-{
- u64 start = entry->file_offset;
- u64 end = start + entry->len - 1;
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22)
- do_sync_file_range(file, start, end, SYNC_FILE_RANGE_WRITE);
-#else
- do_sync_mapping_range(inode->i_mapping, start, end,
- SYNC_FILE_RANGE_WRITE);
-#endif
- wait_event(entry->wait,
- test_bit(BTRFS_ORDERED_COMPLETE, &entry->flags));
-}
-
-static void btrfs_start_ordered_extent(struct inode *inode,
- struct btrfs_ordered_extent *entry, int wait)
+/*
+ * Used to start IO or wait for a given ordered extent to finish.
+ *
+ * If wait is one, this effectively waits on page writeback for all the pages
+ * in the extent, and it waits on the io completion code to insert
+ * metadata into the btree corresponding to the extent
+ */
+void btrfs_start_ordered_extent(struct inode *inode,
+ struct btrfs_ordered_extent *entry,
+ int wait)
{
u64 start = entry->file_offset;
u64 end = start + entry->len - 1;
+ /*
+ * pages in the range can be dirty, clean or writeback. We
+ * start IO on any dirty ones so the wait doesn't stall waiting
+ * for pdflush to find them
+ */
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22)
do_sync_file_range(file, start, end, SYNC_FILE_RANGE_WRITE);
#else
@@ -309,6 +323,9 @@
&entry->flags));
}
+/*
+ * Used to wait on ordered extents across a large range of bytes.
+ */
void btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
{
u64 end;
@@ -349,31 +366,11 @@
}
}
-int btrfs_add_ordered_pending(struct inode *inode,
- struct btrfs_ordered_extent *ordered,
- u64 start, u64 len)
-{
- WARN_ON(1);
- return 0;
-#if 0
- int ret;
- struct btrfs_ordered_inode_tree *tree;
- struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
- tree = &BTRFS_I(inode)->ordered_tree;
- mutex_lock(&tree->mutex);
- if (test_bit(BTRFS_ORDERED_IO_DONE, &ordered->flags)) {
- ret = -EAGAIN;
- goto out;
- }
- set_extent_ordered(io_tree, start, start + len - 1, GFP_NOFS);
- ret = 0;
-out:
- mutex_unlock(&tree->mutex);
- return ret;
-#endif
-}
-
+/*
+ * find an ordered extent corresponding to file_offset. return NULL if
+ * nothing is found, otherwise take a reference on the extent and return it
+ */
struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
u64 file_offset)
{
@@ -397,6 +394,10 @@
return entry;
}
+/*
+ * lookup and return any extent before 'file_offset'. NULL is returned
+ * if none is found
+ */
struct btrfs_ordered_extent *
btrfs_lookup_first_ordered_extent(struct inode * inode, u64 file_offset)
{
@@ -417,6 +418,10 @@
return entry;
}
+/*
+ * After an extent is done, call this to conditionally update the on disk
+ * i_size. i_size is updated to cover any fully written part of the file.
+ */
int btrfs_ordered_update_i_size(struct inode *inode,
struct btrfs_ordered_extent *ordered)
{
@@ -507,6 +512,11 @@
return 0;
}
+/*
+ * search the ordered extents for one corresponding to 'offset' and
+ * try to find a checksum. This is used because we allow pages to
+ * be reclaimed before their checksum is actually put into the btree
+ */
int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u32 *sum)
{
struct btrfs_ordered_sum *ordered_sum;