linux-kernel - [PATCH RFC 4/8] fs: Introduce FALLOC_FL

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Date:   Thu, 15 Sep 2022 09:48:22 -0700
From:   Sarthak Kukreti <sarthakkukreti@...omium.org>
To:     dm-devel@...hat.com, linux-block@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Cc:     Jens Axboe <axboe@...nel.dk>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Bart Van Assche <bvanassche@...gle.com>,
        Daniil Lunev <dlunev@...gle.com>,
        Evan Green <evgreen@...gle.com>,
        Gwendal Grignou <gwendal@...gle.com>,
        Sarthak Kukreti <sarthakkukreti@...omium.org>
Subject: [PATCH RFC 4/8] fs: Introduce FALLOC_FL_PROVISION

From: Sarthak Kukreti <sarthakkukreti@...omium.org>

FALLOC_FL_PROVISION is a new fallocate() allocation mode that
sends a hint to (supported) thinly provisioned block devices to
allocate space for the given range of sectors via REQ_OP_PROVISION.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@...omium.org>
---
 block/fops.c                | 7 ++++++-
 include/linux/falloc.h      | 3 ++-
 include/uapi/linux/falloc.h | 8 ++++++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index b90742595317..a436a7596508 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -605,7 +605,8 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 
 #define	BLKDEV_FALLOC_FL_SUPPORTED					\
 		(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |		\
-		 FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE)
+		 FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE |	\
+		 FALLOC_FL_PROVISION)
 
 static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 			     loff_t len)
@@ -661,6 +662,10 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 		error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
 					     len >> SECTOR_SHIFT, GFP_KERNEL);
 		break;
+	case FALLOC_FL_PROVISION:
+		error = blkdev_issue_provision(bdev, start >> SECTOR_SHIFT,
+					       len >> SECTOR_SHIFT, GFP_KERNEL);
+		break;
 	default:
 		error = -EOPNOTSUPP;
 	}
diff --git a/include/linux/falloc.h b/include/linux/falloc.h
index f3f0b97b1675..a0e506255b20 100644
--- a/include/linux/falloc.h
+++ b/include/linux/falloc.h
@@ -30,7 +30,8 @@ struct space_resv {
 					 FALLOC_FL_COLLAPSE_RANGE |	\
 					 FALLOC_FL_ZERO_RANGE |		\
 					 FALLOC_FL_INSERT_RANGE |	\
-					 FALLOC_FL_UNSHARE_RANGE)
+					 FALLOC_FL_UNSHARE_RANGE |                          \
+					 FALLOC_FL_PROVISION)
 
 /* on ia32 l_start is on a 32-bit boundary */
 #if defined(CONFIG_X86_64)
diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 51398fa57f6c..2d323d113eed 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -77,4 +77,12 @@
  */
 #define FALLOC_FL_UNSHARE_RANGE		0x40
 
+/*
+ * FALLOC_FL_PROVISION acts as a hint for thinly provisioned devices to allocate
+ * blocks for the range/EOF.
+ *
+ * FALLOC_FL_PROVISION can only be used with allocate-mode fallocate.
+ */
+#define FALLOC_FL_PROVISION		0x80
+
 #endif /* _UAPI_FALLOC_H_ */
-- 
2.31.0