When gfs2 does metadata read ahead, currently flags (REQ_RAHEAD | REQ_META)
are used to submit bio. Flag REQ_META is just a hint for block trace, not
for block layer code to handle a bio as metadata request.
When doing read ahead for metadata, A REQ_PRIO flag on the metadata bio
is very informative to block layer code. For example, if bcache is used as
a I/O cache for gfs2, it will be possible for bcache code to cache the
pre-fetched metadata blocks on cache device as well, which may be
probably to improve metadata I/O performance if the following requests
hit the cache.
This patch adds REQ_PRIO flag when submitting a metadata readahead bio.
A meta data read ahead bio may come from I/O requests for bitmap,
directoriesmeta or other general metadata request.
Signed-off-by: Coly Li <colyli@xxxxxxx>
---
fs/gfs2/bmap.c | 5 +++--
fs/gfs2/dir.c | 4 +++-
fs/gfs2/meta_io.c | 4 +++-
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 9fa3aef9a5b3..fa3ea29f39cf 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -291,8 +291,9 @@ static void gfs2_metapath_ra(struct gfs2_glock *gl,
if (trylock_buffer(rabh)) {
if (!buffer_uptodate(rabh)) {
rabh->b_end_io = end_buffer_read_sync;
- submit_bh(REQ_OP_READ, REQ_RAHEAD | REQ_META,
- rabh);
+ submit_bh(REQ_OP_READ,
+ REQ_RAHEAD | REQ_META | REQ_PRIO,
+ rabh);
continue;
}
unlock_buffer(rabh);
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index db427658ccd9..0741e4018f8c 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -1514,7 +1514,9 @@ static void gfs2_dir_readahead(struct inode *inode, unsigned hsize, u32 index,
continue;
}
bh->b_end_io = end_buffer_read_sync;
- submit_bh(REQ_OP_READ, REQ_RAHEAD | REQ_META, bh);
+ submit_bh(REQ_OP_READ,
+ REQ_RAHEAD | REQ_META | REQ_PRIO,
+ bh);
continue;
}
brelse(bh);
diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index fabe1614f879..6103d1c816ef 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -461,7 +461,9 @@ struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen)
bh = gfs2_getbuf(gl, dblock, CREATE);
if (!buffer_uptodate(bh) && !buffer_locked(bh))
- ll_rw_block(REQ_OP_READ, REQ_RAHEAD | REQ_META, 1, &bh);
+ ll_rw_block(REQ_OP_READ,
+ REQ_RAHEAD | REQ_META | REQ_PRIO,
+ 1, &bh);
brelse(bh);
dblock++;
extlen--;
--
2.12.0
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