@@ -1533,6 +1533,27 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
return ret;
}
+/*
+ * Check if we can do nocow write into the range [@pos, @pos + @write_bytes)
+ *
+ * @pos: File offset
+ * @write_bytes: The length to write, will be updated to the nocow writeable
+ * range
+ * @nowait: Whether this function could sleep.
+ *
+ * This function will flush ordered extents in the range to ensure proper
+ * nocow checks for (nowait == false) case.
+ *
+ * Return:
+ * >0 and update @write_bytes if we can do nocow write.
+ * 0 if we can't do nocow write.
+ * -EAGAIN if we can't get the needed lock or there are ordered extents for
+ * (nowait == true) case.
+ * <0 if other error happened.
+ *
+ * NOTE: For wait (nowait==false) calls, callers need to release the drew write
+ * lock of inode->root->snapshot_lock when return value > 0.
+ */
int btrfs_check_can_nocow(struct btrfs_inode *inode, loff_t pos,
size_t *write_bytes, bool nowait)
{
@@ -6952,8 +6952,25 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
}
/*
- * returns 1 when the nocow is safe, < 1 on error, 0 if the
- * block must be cow'd
+ * Check if we can do nocow write into the range [@offset, @offset+ @len)
+ *
+ * @offset: File offset
+ * @len: The length to write, will be updated to the nocow writeable
+ * range
+ * @orig_start: (Optional) Return the original file offset of the file extent
+ * @orig_len: (Optional) Return the original on-disk length of the file extent
+ * @ram_bytes: (Optional) Return the ram_bytes of the file extent
+ *
+ * This function will flush ordered extents in the range to ensure proper
+ * nocow checks for (nowait == false) case.
+ *
+ * Return:
+ * >0 and update @len if we can do nocow write.
+ * 0 if we can't do nocow write.
+ * <0 if error happened.
+ *
+ * NOTE: This only checks the file extents, caller is responsible to wait for
+ * any ordered extents.
*/
noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
u64 *orig_start, u64 *orig_block_len,
These two functions have extra conditions that their callers need to meet, and some not-that-common parameters used for return value. So adding some comments may save reviewers some time. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/file.c | 21 +++++++++++++++++++++ fs/btrfs/inode.c | 21 +++++++++++++++++++-- 2 files changed, 40 insertions(+), 2 deletions(-)