From: Xiubo Li xiubli@redhat.com
commit dc94bb8f271c079f69583d0f12a489aaf5202751 upstream.
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@vger.kernel.org Fixes: 49870056005c ("ceph: convert ceph_readpages to ceph_readahead") Link: https://lore.kernel.org/ceph-devel/20230504082510.247-1-sehuww@mail.scut.edu... Link: https://www.spinics.net/lists/ceph-users/msg76183.html Signed-off-by: Xiubo Li xiubli@redhat.com Reviewed-and-tested-by: Hu Weiwen sehuww@mail.scut.edu.cn Reviewed-by: Milind Changire mchangir@redhat.com Signed-off-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ceph/addr.c | 40 +++++++++++++++++++++++++++++++++------- 1 file changed, 33 insertions(+), 7 deletions(-)
--- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -187,16 +187,42 @@ static void ceph_netfs_expand_readahead( 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)