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gfs2: Stop using glock holder auto-demotion for now

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We're having unresolved issues with the glock holder auto-demotion mechanism
introduced in commit dc732906c2.  This mechanism was assumed to be essential
for avoiding frequent short reads and writes until commit 296abc0d91
("gfs2: No short reads or writes upon glock contention").  Since then,
when the inode glock is lost, it is simply re-acquired and the operation
is resumed.  This means that apart from the performance penalty, we
might as well drop the inode glock before faulting in pages, and
re-acquire it afterwards.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2022-05-11 18:27:12 +02:00
parent fa5dfa645d
commit e1fa9ea85c
1 changed files with 18 additions and 36 deletions
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54
fs/gfs2/file.c
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@ -832,7 +832,6 @@ retry:
ret = gfs2_glock_nq(gh);
if (ret)
goto out_uninit;
retry_under_glock:
pagefault_disable();
to->nofault = true;
ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL,
@ -845,14 +844,10 @@ retry_under_glock:
read = ret;
if (should_fault_in_pages(to, iocb, &prev_count, &window_size)) {
gfs2_holder_allow_demote(gh);
gfs2_glock_dq(gh);
window_size -= fault_in_iov_iter_writeable(to, window_size);
gfs2_holder_disallow_demote(gh);
if (window_size) {
if (gfs2_holder_queued(gh))
goto retry_under_glock;
if (window_size)
goto retry;
}
}
out_unlock:
if (gfs2_holder_queued(gh))
@ -900,7 +895,6 @@ retry:
/* Silently fall back to buffered I/O when writing beyond EOF */
if (iocb->ki_pos + iov_iter_count(from) > i_size_read(&ip->i_inode))
goto out_unlock;
retry_under_glock:
from->nofault = true;
ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL,
@ -916,14 +910,10 @@ retry_under_glock:
written = ret;
if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
gfs2_holder_allow_demote(gh);
gfs2_glock_dq(gh);
window_size -= fault_in_iov_iter_readable(from, window_size);
gfs2_holder_disallow_demote(gh);
if (window_size) {
if (gfs2_holder_queued(gh))
goto retry_under_glock;
if (window_size)
goto retry;
}
}
out_unlock:
if (gfs2_holder_queued(gh))
@ -974,7 +964,6 @@ retry:
ret = gfs2_glock_nq(&gh);
if (ret)
goto out_uninit;
retry_under_glock:
pagefault_disable();
ret = generic_file_read_iter(iocb, to);
pagefault_enable();
@ -984,14 +973,10 @@ retry_under_glock:
read += ret;
if (should_fault_in_pages(to, iocb, &prev_count, &window_size)) {
gfs2_holder_allow_demote(&gh);
gfs2_glock_dq(&gh);
window_size -= fault_in_iov_iter_writeable(to, window_size);
gfs2_holder_disallow_demote(&gh);
if (window_size) {
if (gfs2_holder_queued(&gh))
goto retry_under_glock;
if (window_size)
goto retry;
}
}
out_unlock:
if (gfs2_holder_queued(&gh))
@ -1030,22 +1015,17 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb,
gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, gh);
retry:
if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
window_size -= fault_in_iov_iter_readable(from, window_size);
if (!window_size) {
ret = -EFAULT;
goto out_uninit;
}
from->count = min(from->count, window_size);
}
ret = gfs2_glock_nq(gh);
if (ret)
goto out_uninit;
if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
retry_under_glock:
gfs2_holder_allow_demote(gh);
window_size -= fault_in_iov_iter_readable(from, window_size);
gfs2_holder_disallow_demote(gh);
if (!window_size) {
ret = -EFAULT;
goto out_unlock;
}
if (!gfs2_holder_queued(gh))
goto retry;
from->count = min(from->count, window_size);
}
if (inode == sdp->sd_rindex) {
struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
@ -1073,8 +1053,10 @@ retry_under_glock:
goto out_unlock;
from->count = orig_count - written;
if (should_fault_in_pages(from, iocb, &prev_count, &window_size))
goto retry_under_glock;
if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
gfs2_glock_dq(gh);
goto retry;
}
out_unlock:
if (gfs2_holder_queued(gh))
gfs2_glock_dq(gh);