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Message-Id: <20230503183821.1473305-12-john.g.garry@oracle.com>
Date: Wed, 3 May 2023 18:38:16 +0000
From: John Garry <john.g.garry@...cle.com>
To: axboe@...nel.dk, kbusch@...nel.org, hch@....de, sagi@...mberg.me,
martin.petersen@...cle.com, djwong@...nel.org,
viro@...iv.linux.org.uk, brauner@...nel.org, dchinner@...hat.com,
jejb@...ux.ibm.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-security-module@...r.kernel.org, paul@...l-moore.com,
jmorris@...ei.org, serge@...lyn.com,
John Garry <john.g.garry@...cle.com>
Subject: [PATCH RFC 11/16] fs: iomap: Atomic write support
Add support to create bio's whose bi_sector and bi_size are aligned to and
multiple of atomic_write_unit, respectively.
When we call iomap_dio_bio_iter() -> bio_iov_iter_get_pages() ->
__bio_iov_iter_get_pages(), we trim the bio to a multiple of
atomic_write_unit.
As such, we expect the iomi start and length to have same size and
alignment requirements per iomap_dio_bio_iter() call.
In iomap_dio_bio_iter(), ensure that for a non-dsync iocb that the mapping
is not dirty nor unmapped.
Signed-off-by: John Garry <john.g.garry@...cle.com>
---
fs/iomap/direct-io.c | 72 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 70 insertions(+), 2 deletions(-)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index f771001574d0..37c3c926dfd8 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -36,6 +36,8 @@ struct iomap_dio {
size_t done_before;
bool wait_for_completion;
+ unsigned int atomic_write_unit;
+
union {
/* used during submission and for synchronous completion: */
struct {
@@ -229,9 +231,21 @@ static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
return opflags;
}
+
+/*
+ * Note: For atomic writes, each bio which we create when we iter should have
+ * bi_sector aligned to atomic_write_unit and also its bi_size should be
+ * a multiple of atomic_write_unit.
+ * The call to bio_iov_iter_get_pages() -> __bio_iov_iter_get_pages()
+ * should trim the length to a multiple of atomic_write_unit for us.
+ * This allows us to split each bio later in the block layer to fit
+ * request_queue limit.
+ */
static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
struct iomap_dio *dio)
{
+ bool atomic_write = (dio->iocb->ki_flags & IOCB_ATOMIC) &&
+ (dio->flags & IOMAP_DIO_WRITE);
const struct iomap *iomap = &iter->iomap;
struct inode *inode = iter->inode;
unsigned int fs_block_size = i_blocksize(inode), pad;
@@ -249,6 +263,14 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
!bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
return -EINVAL;
+
+ if (atomic_write && !iocb_is_dsync(dio->iocb)) {
+ if (iomap->flags & IOMAP_F_DIRTY)
+ return -EIO;
+ if (iomap->type != IOMAP_MAPPED)
+ return -EIO;
+ }
+
if (iomap->type == IOMAP_UNWRITTEN) {
dio->flags |= IOMAP_DIO_UNWRITTEN;
need_zeroout = true;
@@ -318,6 +340,10 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
GFP_KERNEL);
bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
bio->bi_ioprio = dio->iocb->ki_ioprio;
+ if (atomic_write) {
+ bio->bi_opf |= REQ_ATOMIC;
+ bio->atomic_write_unit = dio->atomic_write_unit;
+ }
bio->bi_private = dio;
bio->bi_end_io = iomap_dio_bio_end_io;
@@ -492,6 +518,8 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
struct blk_plug plug;
struct iomap_dio *dio;
+ bool is_read = iov_iter_rw(iter) == READ;
+ bool atomic_write = (iocb->ki_flags & IOCB_ATOMIC) && !is_read;
if (!iomi.len)
return NULL;
@@ -500,6 +528,20 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (!dio)
return ERR_PTR(-ENOMEM);
+ if (atomic_write) {
+ /*
+ * Note: This lookup is not proper for a multi-device scenario,
+ * however for current iomap users, the bdev per iter
+ * will be fixed, so "works" for now.
+ */
+ struct super_block *i_sb = inode->i_sb;
+ struct block_device *bdev = i_sb->s_bdev;
+
+ dio->atomic_write_unit =
+ bdev_find_max_atomic_write_alignment(bdev,
+ iomi.pos, iomi.len);
+ }
+
dio->iocb = iocb;
atomic_set(&dio->ref, 1);
dio->size = 0;
@@ -513,7 +555,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->submit.waiter = current;
dio->submit.poll_bio = NULL;
- if (iov_iter_rw(iter) == READ) {
+ if (is_read) {
if (iomi.pos >= dio->i_size)
goto out_free_dio;
@@ -567,7 +609,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (ret)
goto out_free_dio;
- if (iov_iter_rw(iter) == WRITE) {
+ if (!is_read) {
/*
* Try to invalidate cache pages for the range we are writing.
* If this invalidation fails, let the caller fall back to
@@ -592,6 +634,32 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
blk_start_plug(&plug);
while ((ret = iomap_iter(&iomi, ops)) > 0) {
+ if (atomic_write) {
+ const struct iomap *_iomap = &iomi.iomap;
+ loff_t iomi_length = iomap_length(&iomi);
+
+ /*
+ * Ensure length and start address is a multiple of
+ * atomic_write_unit - this is critical. If the length
+ * is not a multiple of atomic_write_unit, then we
+ * cannot create a set of bio's in iomap_dio_bio_iter()
+ * who are each a length which is a multiple of
+ * atomic_write_unit.
+ *
+ * Note: It may be more appropiate to have this check
+ * in iomap_dio_bio_iter()
+ */
+ if ((iomap_sector(_iomap, iomi.pos) << SECTOR_SHIFT) %
+ dio->atomic_write_unit) {
+ ret = -EIO;
+ break;
+ }
+
+ if (iomi_length % dio->atomic_write_unit) {
+ ret = -EIO;
+ break;
+ }
+ }
iomi.processed = iomap_dio_iter(&iomi, dio);
/*
--
2.31.1
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