Btrfs: rework O_DIRECT enospc handling

This changes O_DIRECT write code to mark extents as delalloc
while it is processing them.  Yan Zheng has reworked the
enospc accounting based on tracking delalloc extents and
this makes it much easier to track enospc in the O_DIRECT code.

There are a few space cases with the O_DIRECT code though,
it only sets the EXTENT_DELALLOC bits, instead of doing
EXTENT_DELALLOC | EXTENT_DIRTY | EXTENT_UPTODATE, because
we don't want to mess with clearing the dirty and uptodate
bits when things go wrong.  This is important because there
are no pages in the page cache, so any extent state structs
that we put in the tree won't get freed by releasepage.  We have
to clear them ourselves as the DIO ends.

With this commit, we reserve space at in btrfs_file_aio_write,
and then as each btrfs_direct_IO call progresses it sets
EXTENT_DELALLOC on the range.

btrfs_get_blocks_direct is responsible for clearing the delalloc
at the same time it drops the extent lock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 41 insertions, 11 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 13a4aa2..00aefbd 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5327,8 +5327,9 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
 			return PTR_ERR(em);
 		len = min(len, em->block_len);
 	}
-	unlock_extent(&BTRFS_I(inode)->io_tree, start, start + len - 1,
-		      GFP_NOFS);
+	clear_extent_bit(&BTRFS_I(inode)->io_tree, start, start + len - 1,
+			  EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DIRTY, 1,
+			  0, NULL, GFP_NOFS);
 map:
 	bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
 		inode->i_blkbits;
@@ -5596,14 +5597,18 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
 	struct btrfs_ordered_extent *ordered;
+	struct extent_state *cached_state = NULL;
 	u64 lockstart, lockend;
 	ssize_t ret;
+	int writing = rw & WRITE;
+	int write_bits = 0;
 
 	lockstart = offset;
 	lockend = offset + iov_length(iov, nr_segs) - 1;
+
 	while (1) {
-		lock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend,
-			    GFP_NOFS);
+		lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+				 0, &cached_state, GFP_NOFS);
 		/*
 		 * We're concerned with the entire range that we're going to be
 		 * doing DIO to, so we need to make sure theres no ordered
@@ -5613,29 +5618,54 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 						     lockend - lockstart + 1);
 		if (!ordered)
 			break;
-		unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend,
-			      GFP_NOFS);
+		unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+				     &cached_state, GFP_NOFS);
 		btrfs_start_ordered_extent(inode, ordered, 1);
 		btrfs_put_ordered_extent(ordered);
 		cond_resched();
 	}
 
+	/*
+	 * we don't use btrfs_set_extent_delalloc because we don't want
+	 * the dirty or uptodate bits
+	 */
+	if (writing) {
+		write_bits = EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING;
+		ret = set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+				     EXTENT_DELALLOC, 0, NULL, &cached_state,
+				     GFP_NOFS);
+		if (ret) {
+			clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
+					 lockend, EXTENT_LOCKED | write_bits,
+					 1, 0, &cached_state, GFP_NOFS);
+			goto out;
+		}
+	}
+
+	free_extent_state(cached_state);
+	cached_state = NULL;
+
 	ret = __blockdev_direct_IO(rw, iocb, inode, NULL, iov, offset, nr_segs,
 				   btrfs_get_blocks_direct, NULL,
 				   btrfs_submit_direct, 0);
 
 	if (ret < 0 && ret != -EIOCBQUEUED) {
-		unlock_extent(&BTRFS_I(inode)->io_tree, offset,
-			      offset + iov_length(iov, nr_segs) - 1, GFP_NOFS);
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, offset,
+			      offset + iov_length(iov, nr_segs) - 1,
+			      EXTENT_LOCKED | write_bits, 1, 0,
+			      &cached_state, GFP_NOFS);
 	} else if (ret >= 0 && ret < iov_length(iov, nr_segs)) {
 		/*
 		 * We're falling back to buffered, unlock the section we didn't
 		 * do IO on.
 		 */
-		unlock_extent(&BTRFS_I(inode)->io_tree, offset + ret,
-			      offset + iov_length(iov, nr_segs) - 1, GFP_NOFS);
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, offset + ret,
+			      offset + iov_length(iov, nr_segs) - 1,
+			      EXTENT_LOCKED | write_bits, 1, 0,
+			      &cached_state, GFP_NOFS);
 	}
-
+out:
+	free_extent_state(cached_state);
 	return ret;
 }