[PATCH 11/11] xfs: flush speculative space allocations when we run out of space

Darrick J. Wong
2021-01-23T18:53:48Z

From: Darrick J. Wong <djwong@kernel.org>

If a fs modification (creation, file write, reflink, etc.) is unable to
reserve enough space to handle the modification, try clearing whatever
space the filesystem might have been hanging onto in the hopes of
speeding up the filesystem. The flushing behavior will become
particularly important when we add deferred inode inactivation because
that will increase the amount of space that isn't actively tied to user
data.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/xfs_trans.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index e72730f85af1..2b92a4084bb8 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -20,6 +20,8 @@
#include "xfs_trace.h"
#include "xfs_error.h"
#include "xfs_defer.h"
+#include "xfs_inode.h"
+#include "xfs_icache.h"

kmem_zone_t *xfs_trans_zone;

@@ -256,8 +258,10 @@ xfs_trans_alloc(
struct xfs_trans **tpp)
{
struct xfs_trans *tp;
+ unsigned int tries = 1;
int error;

+retry:
/*
* Allocate the handle before we do our freeze accounting and setting up
* GFP_NOFS allocation context so that we avoid lockdep false positives
@@ -285,6 +289,22 @@ xfs_trans_alloc(
tp->t_firstblock = NULLFSBLOCK;

error = xfs_trans_reserve(tp, resp, blocks, rtextents);
+ if (error == -ENOSPC && tries > 0) {
+ xfs_trans_cancel(tp);
+
+ /*
+ * We weren't able to reserve enough space for the transaction.
+ * Flush the other speculative space allocations to free space.
+ * Do not perform a synchronous scan because callers can hold
+ * other locks.
+ */
+ error = xfs_blockgc_free_space(mp, NULL);
+ if (error)
+ return error;
+
+ tries--;
+ goto retry;
+ }
if (error) {
xfs_trans_cancel(tp);
return error;