[PATCH AUTOSEL 5.4 287/330] btrfs: fix double __endio_write_update_ordered in direct I/O

Sasha Levin
2020-09-18T02:55:34Z

From: Omar Sandoval <osandov@fb.com>

[ Upstream commit c36cac28cb94e58f7e21ff43bdc6064346dab32c ]

In btrfs_submit_direct(), if we fail to allocate the btrfs_dio_private,
we complete the ordered extent range. However, we don't mark that the
range doesn't need to be cleaned up from btrfs_direct_IO() until later.
Therefore, if we fail to allocate the btrfs_dio_private, we complete the
ordered extent range twice. We could fix this by updating
unsubmitted_oe_range earlier, but it's cleaner to reorganize the code so
that creating the btrfs_dio_private and submitting the bios are
separate, and once the btrfs_dio_private is created, cleanup always
happens through the btrfs_dio_private.

The logic around unsubmitted_oe_range_end and unsubmitted_oe_range_start
is really subtle. We have the following:

1. btrfs_direct_IO sets those two to the same value.

2. When we call __blockdev_direct_IO unless
btrfs_get_blocks_direct->btrfs_get_blocks_direct_write is called to
modify unsubmitted_oe_range_start so that start < end. Cleanup
won't happen.

3. We come into btrfs_submit_direct - if it dip allocation fails we'd
return with oe_range_end now modified so cleanup will happen.

4. If we manage to allocate the dip we reset the unsubmitted range
members to be equal so that cleanup happens from
btrfs_endio_direct_write.

This 4-step logic is not really obvious, especially given it's scattered
across 3 functions.

Fixes: f28a49287817 ("Btrfs: fix leaking of ordered extents after direct IO write error")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
[ add range start/end logic explanation from Nikolay ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/inode.c | 178 +++++++++++++++++++----------------------------
1 file changed, 70 insertions(+), 108 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 9ac40991a6405..e9787b7b943a2 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8586,14 +8586,64 @@ err:
return ret;
}

-static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
+/*
+ * If this succeeds, the btrfs_dio_private is responsible for cleaning up locked
+ * or ordered extents whether or not we submit any bios.
+ */
+static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio,
+ struct inode *inode,
+ loff_t file_offset)
{
- struct inode *inode = dip->inode;
+ const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
+ struct btrfs_dio_private *dip;
+ struct bio *bio;
+
+ dip = kzalloc(sizeof(*dip), GFP_NOFS);
+ if (!dip)
+ return NULL;
+
+ bio = btrfs_bio_clone(dio_bio);
+ bio->bi_private = dip;
+ btrfs_io_bio(bio)->logical = file_offset;
+
+ dip->private = dio_bio->bi_private;
+ dip->inode = inode;
+ dip->logical_offset = file_offset;
+ dip->bytes = dio_bio->bi_iter.bi_size;
+ dip->disk_bytenr = (u64)dio_bio->bi_iter.bi_sector << 9;
+ dip->orig_bio = bio;
+ dip->dio_bio = dio_bio;
+ atomic_set(&dip->pending_bios, 1);
+
+ if (write) {
+ struct btrfs_dio_data *dio_data = current->journal_info;
+
+ /*
+ * Setting range start and end to the same value means that
+ * no cleanup will happen in btrfs_direct_IO
+ */
+ dio_data->unsubmitted_oe_range_end = dip->logical_offset +
+ dip->bytes;
+ dio_data->unsubmitted_oe_range_start =
+ dio_data->unsubmitted_oe_range_end;
+
+ bio->bi_end_io = btrfs_endio_direct_write;
+ } else {
+ bio->bi_end_io = btrfs_endio_direct_read;
+ dip->subio_endio = btrfs_subio_endio_read;
+ }
+ return dip;
+}
+
+static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
+ loff_t file_offset)
+{
+ const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ struct btrfs_dio_private *dip;
struct bio *bio;
- struct bio *orig_bio = dip->orig_bio;
- u64 start_sector = orig_bio->bi_iter.bi_sector;
- u64 file_offset = dip->logical_offset;
+ struct bio *orig_bio;
+ u64 start_sector;
int async_submit = 0;
u64 submit_len;
int clone_offset = 0;
@@ -8602,11 +8652,24 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
blk_status_t status;
struct btrfs_io_geometry geom;

+ dip = btrfs_create_dio_private(dio_bio, inode, file_offset);
+ if (!dip) {
+ if (!write) {
+ unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,
+ file_offset + dio_bio->bi_iter.bi_size - 1);
+ }
+ dio_bio->bi_status = BLK_STS_RESOURCE;
+ dio_end_io(dio_bio);
+ return;
+ }
+
+ orig_bio = dip->orig_bio;
+ start_sector = orig_bio->bi_iter.bi_sector;
submit_len = orig_bio->bi_iter.bi_size;
ret = btrfs_get_io_geometry(fs_info, btrfs_op(orig_bio),
start_sector << 9, submit_len, &geom);
if (ret)
- return -EIO;
+ goto out_err;

if (geom.len >= submit_len) {
bio = orig_bio;
@@ -8669,7 +8732,7 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
submit:
status = btrfs_submit_dio_bio(bio, inode, file_offset, async_submit);
if (!status)
- return 0;
+ return;

if (bio != orig_bio)
bio_put(bio);
@@ -8683,107 +8746,6 @@ out_err:
*/
if (atomic_dec_and_test(&dip->pending_bios))
bio_io_error(dip->orig_bio);
-
- /* bio_end_io() will handle error, so we needn't return it */
- return 0;
-}
-
-static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
- loff_t file_offset)
-{
- struct btrfs_dio_private *dip = NULL;
- struct bio *bio = NULL;
- struct btrfs_io_bio *io_bio;
- bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
- int ret = 0;
-
- bio = btrfs_bio_clone(dio_bio);
-
- dip = kzalloc(sizeof(*dip), GFP_NOFS);
- if (!dip) {
- ret = -ENOMEM;
- goto free_ordered;
- }
-
- dip->private = dio_bio->bi_private;
- dip->inode = inode;
- dip->logical_offset = file_offset;
- dip->bytes = dio_bio->bi_iter.bi_size;
- dip->disk_bytenr = (u64)dio_bio->bi_iter.bi_sector << 9;
- bio->bi_private = dip;
- dip->orig_bio = bio;
- dip->dio_bio = dio_bio;
- atomic_set(&dip->pending_bios, 1);
- io_bio = btrfs_io_bio(bio);
- io_bio->logical = file_offset;
-
- if (write) {
- bio->bi_end_io = btrfs_endio_direct_write;
- } else {
- bio->bi_end_io = btrfs_endio_direct_read;
- dip->subio_endio = btrfs_subio_endio_read;
- }
-
- /*
- * Reset the range for unsubmitted ordered extents (to a 0 length range)
- * even if we fail to submit a bio, because in such case we do the
- * corresponding error handling below and it must not be done a second
- * time by btrfs_direct_IO().
- */
- if (write) {
- struct btrfs_dio_data *dio_data = current->journal_info;
-
- dio_data->unsubmitted_oe_range_end = dip->logical_offset +
- dip->bytes;
- dio_data->unsubmitted_oe_range_start =
- dio_data->unsubmitted_oe_range_end;
- }
-
- ret = btrfs_submit_direct_hook(dip);
- if (!ret)
- return;
-
- btrfs_io_bio_free_csum(io_bio);
-
-free_ordered:
- /*
- * If we arrived here it means either we failed to submit the dip
- * or we either failed to clone the dio_bio or failed to allocate the
- * dip. If we cloned the dio_bio and allocated the dip, we can just
- * call bio_endio against our io_bio so that we get proper resource
- * cleanup if we fail to submit the dip, otherwise, we must do the
- * same as btrfs_endio_direct_[write|read] because we can't call these
- * callbacks - they require an allocated dip and a clone of dio_bio.
- */
- if (bio && dip) {
- bio_io_error(bio);
- /*
- * The end io callbacks free our dip, do the final put on bio
- * and all the cleanup and final put for dio_bio (through
- * dio_end_io()).
- */
- dip = NULL;
- bio = NULL;
- } else {
- if (write)
- __endio_write_update_ordered(inode,
- file_offset,
- dio_bio->bi_iter.bi_size,
- false);
- else
- unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,
- file_offset + dio_bio->bi_iter.bi_size - 1);
-
- dio_bio->bi_status = BLK_STS_IOERR;
- /*
- * Releases and cleans up our dio_bio, no need to bio_put()
- * nor bio_endio()/bio_io_error() against dio_bio.
- */
- dio_end_io(dio_bio);
- }
- if (bio)
- bio_put(bio);
- kfree(dip);
}

static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
--
2.25.1