From 48190803b320f34beaa6e46f3b94cc59915fe308 Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Wed, 4 May 2022 23:37:30 +0200 Subject: [PATCH] gfs2: buffered write prefaulting In gfs2_file_buffered_write, to increase the likelihood that all the user memory we're trying to write will be resident in memory, carry out the write in chunks and fault in each chunk of user memory before trying to write it. Otherwise, some workloads will trigger frequent short "internal" writes, causing filesystem blocks to be allocated and then partially deallocated again when writing into holes, which is wasteful and breaks reservations. Neither the chunked writes nor any of the short "internal" writes are user visible. Signed-off-by: Andreas Gruenbacher --- fs/gfs2/file.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c index 11c46407d4a87..5eda1bcc85e37 100644 --- a/fs/gfs2/file.c +++ b/fs/gfs2/file.c @@ -778,7 +778,7 @@ static inline bool should_fault_in_pages(struct iov_iter *i, size_t count = iov_iter_count(i); size_t size, offs; - if (likely(!count)) + if (!count) return false; if (!iter_is_iovec(i)) return false; @@ -1033,7 +1033,20 @@ retry: 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); @@ -1060,17 +1073,8 @@ retry_under_glock: goto out_unlock; from->count = orig_count - written; - if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) { - gfs2_holder_allow_demote(gh); - window_size -= fault_in_iov_iter_readable(from, window_size); - gfs2_holder_disallow_demote(gh); - if (window_size) { - from->count = min(from->count, window_size); - if (gfs2_holder_queued(gh)) - goto retry_under_glock; - goto retry; - } - } + if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) + goto retry_under_glock; out_unlock: if (gfs2_holder_queued(gh)) gfs2_glock_dq(gh); -- 2.39.5