gfs2: More gfs2_find_jhead fixes

It turns out that when extending an existing bio, gfs2_find_jhead fails to
check if the block number is consecutive, which leads to incorrect reads for
fragmented journals.

In addition, limit the maximum bio size to an arbitrary value of 2 megabytes:
since commit 07173c3ec276 ("block: enable multipage bvecs"), if we just keep
adding pages until bio_add_page fails, bios will grow much larger than useful,
which pins more memory than necessary with barely any additional performance
gains.

Fixes: f4686c26ecc3 ("gfs2: read journal in large chunks")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 5ea9675..48b54ec 100644 (file)
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -263,7 +263,7 @@ static struct bio *gfs2_log_alloc_bio(struct gfs2_sbd *sdp, u64 blkno,
        struct super_block *sb = sdp->sd_vfs;
        struct bio *bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
 
-       bio->bi_iter.bi_sector = blkno << (sb->s_blocksize_bits - 9);
+       bio->bi_iter.bi_sector = blkno << sdp->sd_fsb2bb_shift;
        bio_set_dev(bio, sb->s_bdev);
        bio->bi_end_io = end_io;
        bio->bi_private = sdp;
@@ -509,7 +509,7 @@ int gfs2_find_jhead(struct gfs2_jdesc *jd, struct gfs2_log_header_host *head,
        unsigned int bsize = sdp->sd_sb.sb_bsize, off;
        unsigned int bsize_shift = sdp->sd_sb.sb_bsize_shift;
        unsigned int shift = PAGE_SHIFT - bsize_shift;
-       unsigned int readahead_blocks = BIO_MAX_PAGES << shift;
+       unsigned int max_bio_size = 2 * 1024 * 1024;
        struct gfs2_journal_extent *je;
        int sz, ret = 0;
        struct bio *bio = NULL;
@@ -537,12 +537,17 @@ int gfs2_find_jhead(struct gfs2_jdesc *jd, struct gfs2_log_header_host *head,
                                off = 0;
                        }
 
-                       if (!bio || (bio_chained && !off)) {
+                       if (!bio || (bio_chained && !off) ||
+                           bio->bi_iter.bi_size >= max_bio_size) {
                                /* start new bio */
                        } else {
-                               sz = bio_add_page(bio, page, bsize, off);
-                               if (sz == bsize)
-                                       goto block_added;
+                               sector_t sector = dblock << sdp->sd_fsb2bb_shift;
+
+                               if (bio_end_sector(bio) == sector) {
+                                       sz = bio_add_page(bio, page, bsize, off);
+                                       if (sz == bsize)
+                                               goto block_added;
+                               }
                                if (off) {
                                        unsigned int blocks =
                                                (PAGE_SIZE - off) >> bsize_shift;
@@ -568,7 +573,7 @@ block_added:
                        off += bsize;
                        if (off == PAGE_SIZE)
                                page = NULL;
-                       if (blocks_submitted < blocks_read + readahead_blocks) {
+                       if (blocks_submitted < 2 * max_bio_size >> bsize_shift) {
                                /* Keep at least one bio in flight */
                                continue;
                        }