[PATCH 07/12] xfs: don't preallocate a transaction for file size updates

Christoph Hellwig
2019-06-24T05:53:58Z

We have historically decided that we want to preallocate the xfs_trans
structure at writeback time so that we don't have to allocate on in
the I/O completion handler. But we treat unwrittent extent and COW
fork conversions different already, which proves that the transaction
allocations in the end I/O handler are not a problem. Removing the
preallocation gets rid of a lot of corner case code, and also ensures
we only allocate one and log a transaction when actually required,
as the ioend merging can reduce the number of actual i_size updates
significantly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/xfs_aops.c | 110 +++++-----------------------------------------
fs/xfs/xfs_aops.h | 1 -
2 files changed, 12 insertions(+), 99 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 633baaaff7ae..017b87b7765f 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -130,44 +130,23 @@ static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
XFS_I(ioend->io_inode)->i_d.di_size;
}

-STATIC int
-xfs_setfilesize_trans_alloc(
- struct xfs_ioend *ioend)
-{
- struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount;
- struct xfs_trans *tp;
- int error;
-
- error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
- if (error)
- return error;
-
- ioend->io_append_trans = tp;
-
- /*
- * We may pass freeze protection with a transaction. So tell lockdep
- * we released it.
- */
- __sb_writers_release(ioend->io_inode->i_sb, SB_FREEZE_FS);
- /*
- * We hand off the transaction to the completion thread now, so
- * clear the flag here.
- */
- current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
- return 0;
-}
-
/*
* Update on-disk file size now that data has been written to disk.
*/
-STATIC int
-__xfs_setfilesize(
+int
+xfs_setfilesize(
struct xfs_inode *ip,
- struct xfs_trans *tp,
xfs_off_t offset,
size_t size)
{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
xfs_fsize_t isize;
+ int error;
+
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
+ if (error)
+ return error;

xfs_ilock(ip, XFS_ILOCK_EXCL);
isize = xfs_new_eof(ip, offset + size);
@@ -186,48 +165,6 @@ __xfs_setfilesize(
return xfs_trans_commit(tp);
}

-int
-xfs_setfilesize(
- struct xfs_inode *ip,
- xfs_off_t offset,
- size_t size)
-{
- struct xfs_mount *mp = ip->i_mount;
- struct xfs_trans *tp;
- int error;
-
- error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
- if (error)
- return error;
-
- return __xfs_setfilesize(ip, tp, offset, size);
-}
-
-STATIC int
-xfs_setfilesize_ioend(
- struct xfs_ioend *ioend,
- int error)
-{
- struct xfs_inode *ip = XFS_I(ioend->io_inode);
- struct xfs_trans *tp = ioend->io_append_trans;
-
- /*
- * The transaction may have been allocated in the I/O submission thread,
- * thus we need to mark ourselves as being in a transaction manually.
- * Similarly for freeze protection.
- */
- current_set_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
- __sb_writers_acquired(VFS_I(ip)->i_sb, SB_FREEZE_FS);
-
- /* we abort the update if there was an IO error */
- if (error) {
- xfs_trans_cancel(tp);
- return error;
- }
-
- return __xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
-}
-
/*
* IO write completion.
*/
@@ -267,12 +204,9 @@ xfs_end_ioend(
error = xfs_reflink_end_cow(ip, offset, size);
else if (ioend->io_type == IOMAP_UNWRITTEN)
error = xfs_iomap_write_unwritten(ip, offset, size, false);
- else
- ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);
-
+ if (!error && xfs_ioend_is_append(ioend))
+ error = xfs_setfilesize(ip, offset, size);
done:
- if (ioend->io_append_trans)
- error = xfs_setfilesize_ioend(ioend, error);
list_replace_init(&ioend->io_list, &ioend_list);
xfs_destroy_ioend(ioend, error);

@@ -307,8 +241,6 @@ xfs_ioend_can_merge(
return false;
if (ioend->io_offset + ioend->io_size != next->io_offset)
return false;
- if (xfs_ioend_is_append(ioend) != xfs_ioend_is_append(next))
- return false;
return true;
}

@@ -320,7 +252,6 @@ xfs_ioend_try_merge(
{
struct xfs_ioend *next_ioend;
int ioend_error;
- int error;

if (list_empty(more_ioends))
return;
@@ -334,10 +265,6 @@ xfs_ioend_try_merge(
break;
list_move_tail(&next_ioend->io_list, &ioend->io_list);
ioend->io_size += next_ioend->io_size;
- if (ioend->io_append_trans) {
- error = xfs_setfilesize_ioend(next_ioend, 1);
- ASSERT(error == 1);
- }
}
}

@@ -398,7 +325,7 @@ xfs_end_bio(

if (ioend->io_fork == XFS_COW_FORK ||
ioend->io_type == IOMAP_UNWRITTEN ||
- ioend->io_append_trans != NULL) {
+ xfs_ioend_is_append(ioend)) {
spin_lock_irqsave(&ip->i_ioend_lock, flags);
if (list_empty(&ip->i_ioend_list))
WARN_ON_ONCE(!queue_work(mp->m_unwritten_workqueue,
@@ -660,18 +587,6 @@ xfs_submit_ioend(
memalloc_nofs_restore(nofs_flag);
}

- /* Reserve log space if we might write beyond the on-disk inode size. */
- if (!status &&
- (ioend->io_fork == XFS_COW_FORK ||
- ioend->io_type != IOMAP_UNWRITTEN) &&
- xfs_ioend_is_append(ioend) &&
- !ioend->io_append_trans) {
- unsigned nofs_flag = memalloc_nofs_save();
-
- status = xfs_setfilesize_trans_alloc(ioend);
- memalloc_nofs_restore(nofs_flag);
- }
-
ioend->io_bio->bi_private = ioend;
ioend->io_bio->bi_end_io = xfs_end_bio;

@@ -715,7 +630,6 @@ xfs_alloc_ioend(
ioend->io_inode = inode;
ioend->io_size = 0;
ioend->io_offset = offset;
- ioend->io_append_trans = NULL;
ioend->io_bio = bio;
return ioend;
}
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index 72e30d1c3bdf..23c087f0bcbf 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -18,7 +18,6 @@ struct xfs_ioend {
struct inode *io_inode; /* file being written to */
size_t io_size; /* size of the extent */
xfs_off_t io_offset; /* offset in the file */
- struct xfs_trans *io_append_trans;/* xact. for size update */
struct bio *io_bio; /* bio being built */
struct bio io_inline_bio; /* MUST BE LAST! */
};
--
2.20.1