[PATCH 5.5 07/23] gfs2: Another gfs2_find_jhead fix

Greg Kroah-Hartman
2020-02-03T16:38:17Z

From: Andreas Gruenbacher <agruenba@redhat.com>

commit eed0f953b90e86e765197a1dad06bb48aedc27fe upstream.

On filesystems with a block size smaller than the page size,
gfs2_find_jhead can split a page across two bios (for example, when
blocks are not allocated consecutively). When that happens, the first
bio that completes will unlock the page in its bi_end_io handler even
though the page hasn't been read completely yet. Fix that by using a
chained bio for the rest of the page.

While at it, clean up the sector calculation logic in
gfs2_log_alloc_bio. In gfs2_find_jhead, simplify the disk block and
offset calculation logic and fix a variable name.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/gfs2/lops.c | 68 ++++++++++++++++++++++++++++++++++++---------------------
1 file changed, 44 insertions(+), 24 deletions(-)

--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -259,7 +259,7 @@ static struct bio *gfs2_log_alloc_bio(st
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 >> 9);
+ bio->bi_iter.bi_sector = blkno << (sb->s_blocksize_bits - 9);
bio_set_dev(bio, sb->s_bdev);
bio->bi_end_io = end_io;
bio->bi_private = sdp;
@@ -472,6 +472,20 @@ static void gfs2_jhead_process_page(stru
put_page(page); /* Once more for find_or_create_page */
}

+static struct bio *gfs2_chain_bio(struct bio *prev, unsigned int nr_iovecs)
+{
+ struct bio *new;
+
+ new = bio_alloc(GFP_NOIO, nr_iovecs);
+ bio_copy_dev(new, prev);
+ new->bi_iter.bi_sector = bio_end_sector(prev);
+ new->bi_opf = prev->bi_opf;
+ new->bi_write_hint = prev->bi_write_hint;
+ bio_chain(new, prev);
+ submit_bio(prev);
+ return new;
+}
+
/**
* gfs2_find_jhead - find the head of a log
* @jd: The journal descriptor
@@ -488,15 +502,15 @@ int gfs2_find_jhead(struct gfs2_jdesc *j
struct gfs2_sbd *sdp = GFS2_SB(jd->jd_inode);
struct address_space *mapping = jd->jd_inode->i_mapping;
unsigned int block = 0, blocks_submitted = 0, blocks_read = 0;
- unsigned int bsize = sdp->sd_sb.sb_bsize;
+ 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 readhead_blocks = BIO_MAX_PAGES << shift;
+ unsigned int readahead_blocks = BIO_MAX_PAGES << shift;
struct gfs2_journal_extent *je;
int sz, ret = 0;
struct bio *bio = NULL;
struct page *page = NULL;
- bool done = false;
+ bool bio_chained = false, done = false;
errseq_t since;

memset(head, 0, sizeof(*head));
@@ -505,9 +519,9 @@ int gfs2_find_jhead(struct gfs2_jdesc *j

since = filemap_sample_wb_err(mapping);
list_for_each_entry(je, &jd->extent_list, list) {
- for (; block < je->lblock + je->blocks; block++) {
- u64 dblock;
+ u64 dblock = je->dblock;

+ for (; block < je->lblock + je->blocks; block++, dblock++) {
if (!page) {
page = find_or_create_page(mapping,
block >> shift, GFP_NOFS);
@@ -516,35 +530,41 @@ int gfs2_find_jhead(struct gfs2_jdesc *j
done = true;
goto out;
}
+ off = 0;
}

- if (bio) {
- unsigned int off;
-
- off = (block << bsize_shift) & ~PAGE_MASK;
+ if (!bio || (bio_chained && !off)) {
+ /* start new bio */
+ } else {
sz = bio_add_page(bio, page, bsize, off);
- if (sz == bsize) { /* block added */
- if (off + bsize == PAGE_SIZE) {
- page = NULL;
- goto page_added;
- }
- continue;
+ if (sz == bsize)
+ goto block_added;
+ if (off) {
+ unsigned int blocks =
+ (PAGE_SIZE - off) >> bsize_shift;
+
+ bio = gfs2_chain_bio(bio, blocks);
+ bio_chained = true;
+ goto add_block_to_new_bio;
}
+ }
+
+ if (bio) {
blocks_submitted = block + 1;
submit_bio(bio);
- bio = NULL;
}

- dblock = je->dblock + (block - je->lblock);
bio = gfs2_log_alloc_bio(sdp, dblock, gfs2_end_log_read);
bio->bi_opf = REQ_OP_READ;
- sz = bio_add_page(bio, page, bsize, 0);
- gfs2_assert_warn(sdp, sz == bsize);
- if (bsize == PAGE_SIZE)
+ bio_chained = false;
+add_block_to_new_bio:
+ sz = bio_add_page(bio, page, bsize, off);
+ BUG_ON(sz != bsize);
+block_added:
+ off += bsize;
+ if (off == PAGE_SIZE)
page = NULL;
-
-page_added:
- if (blocks_submitted < blocks_read + readhead_blocks) {
+ if (blocks_submitted < blocks_read + readahead_blocks) {
/* Keep at least one bio in flight */
continue;
}