The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x dc94bb8f271c079f69583d0f12a489aaf5202751 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023072116-grading-unplanned-fd32@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: dc94bb8f271c ("ceph: fix blindly expanding the readahead windows") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From dc94bb8f271c079f69583d0f12a489aaf5202751 Mon Sep 17 00:00:00 2001 From: Xiubo Li <xiubli@xxxxxxxxxx> Date: Thu, 4 May 2023 19:00:42 +0800 Subject: [PATCH] ceph: fix blindly expanding the readahead windows Blindly expanding the readahead windows will cause unneccessary pagecache thrashing and also will introduce the network workload. We should disable expanding the windows if the readahead is disabled and also shouldn't expand the windows too much. Expanding forward firstly instead of expanding backward for possible sequential reads. Bound `rreq->len` to the actual file size to restore the previous page cache usage. The posix_fadvise may change the maximum size of a file readahead. Cc: stable@xxxxxxxxxxxxxxx Fixes: 49870056005c ("ceph: convert ceph_readpages to ceph_readahead") Link: https://lore.kernel.org/ceph-devel/20230504082510.247-1-sehuww@xxxxxxxxxxxxxxxx Link: https://www.spinics.net/lists/ceph-users/msg76183.html Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> Reviewed-and-tested-by: Hu Weiwen <sehuww@xxxxxxxxxxxxxxxx> Reviewed-by: Milind Changire <mchangir@xxxxxxxxxx> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index 19c4f08454d2..59cbfb80edbd 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -187,16 +187,42 @@ static void ceph_netfs_expand_readahead(struct netfs_io_request *rreq) struct inode *inode = rreq->inode; struct ceph_inode_info *ci = ceph_inode(inode); struct ceph_file_layout *lo = &ci->i_layout; + unsigned long max_pages = inode->i_sb->s_bdi->ra_pages; + loff_t end = rreq->start + rreq->len, new_end; + struct ceph_netfs_request_data *priv = rreq->netfs_priv; + unsigned long max_len; u32 blockoff; - u64 blockno; - /* Expand the start downward */ - blockno = div_u64_rem(rreq->start, lo->stripe_unit, &blockoff); - rreq->start = blockno * lo->stripe_unit; - rreq->len += blockoff; + if (priv) { + /* Readahead is disabled by posix_fadvise POSIX_FADV_RANDOM */ + if (priv->file_ra_disabled) + max_pages = 0; + else + max_pages = priv->file_ra_pages; - /* Now, round up the length to the next block */ - rreq->len = roundup(rreq->len, lo->stripe_unit); + } + + /* Readahead is disabled */ + if (!max_pages) + return; + + max_len = max_pages << PAGE_SHIFT; + + /* + * Try to expand the length forward by rounding up it to the next + * block, but do not exceed the file size, unless the original + * request already exceeds it. + */ + new_end = min(round_up(end, lo->stripe_unit), rreq->i_size); + if (new_end > end && new_end <= rreq->start + max_len) + rreq->len = new_end - rreq->start; + + /* Try to expand the start downward */ + div_u64_rem(rreq->start, lo->stripe_unit, &blockoff); + if (rreq->len + blockoff <= max_len) { + rreq->start -= blockoff; + rreq->len += blockoff; + } } static bool ceph_netfs_clamp_length(struct netfs_io_subrequest *subreq)
