@@ -9078,7 +9078,7 @@ static ssize_t btrfs_encoded_read_inline(
}
struct btrfs_encoded_read_private {
- struct completion done;
+ struct completion *sync_reads;
void *uring_ctx;
refcount_t pending_refs;
blk_status_t status;
@@ -9090,12 +9090,12 @@ static void btrfs_encoded_read_endio(struct btrfs_bio *bbio)
if (bbio->bio.bi_status) {
/*
- * The memory barrier implied by the atomic_dec_return() here
- * pairs with the memory barrier implied by the
- * atomic_dec_return() or io_wait_event() in
- * btrfs_encoded_read_regular_fill_pages() to ensure that this
- * write is observed before the load of status in
- * btrfs_encoded_read_regular_fill_pages().
+ * The memory barrier implied by the
+ * refcount_dec_and_test() here pairs with the memory
+ * barrier implied by the refcount_dec_and_test() in
+ * btrfs_encoded_read_regular_fill_pages() to ensure
+ * that this write is observed before the load of
+ * status in btrfs_encoded_read_regular_fill_pages().
*/
WRITE_ONCE(priv->status, bbio->bio.bi_status);
}
@@ -9106,7 +9106,7 @@ static void btrfs_encoded_read_endio(struct btrfs_bio *bbio)
btrfs_uring_read_extent_endio(priv->uring_ctx, err);
kfree(priv);
} else {
- complete(&priv->done);
+ complete(priv->sync_reads);
}
}
bio_put(&bbio->bio);
@@ -9117,16 +9117,22 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
struct page **pages, void *uring_ctx)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
- struct btrfs_encoded_read_private *priv;
+ struct btrfs_encoded_read_private *priv, sync_priv;
+ struct completion sync_reads;
unsigned long i = 0;
struct btrfs_bio *bbio;
int ret;
- priv = kmalloc(sizeof(struct btrfs_encoded_read_private), GFP_NOFS);
- if (!priv)
- return -ENOMEM;
+ if (uring_ctx) {
+ priv = kmalloc(sizeof(struct btrfs_encoded_read_private), GFP_NOFS);
+ if (!priv)
+ return -ENOMEM;
+ } else {
+ priv = &sync_priv;
+ init_completion(&sync_reads);
+ priv->sync_reads = &sync_reads;
+ }
- init_completion(&priv->done);
refcount_set(&priv->pending_refs, 1);
priv->status = 0;
priv->uring_ctx = uring_ctx;
@@ -9169,11 +9175,9 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
return -EIOCBQUEUED;
} else {
if (!refcount_dec_and_test(&priv->pending_refs))
- wait_for_completion_io(&priv->done);
+ wait_for_completion_io(&sync_reads);
/* See btrfs_encoded_read_endio() for ordering. */
- ret = blk_status_to_errno(READ_ONCE(priv->status));
- kfree(priv);
- return ret;
+ return blk_status_to_errno(READ_ONCE(priv->status));
}
}
Only allocate the `priv` struct from slab for asynchronous mode. There's no need to allocate an object from slab in the synchronous mode. In such a case stack can be happily used as it used to be before 68d3b27e05c7 ("btrfs: move priv off stack in btrfs_encoded_read_regular_fill_pages()") which was a preparation for the async mode. While at it, fix the comment to reflect the atomic => refcount change in d29662695ed7 ("btrfs: fix use-after-free waiting for encoded read endios"). Signed-off-by: Daniel Vacek <neelx@suse.com> --- v2 reduces the patch only to functional changes as suggested by Johannes and Dave. fs/btrfs/inode.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-)