[PATCH 4.15 073/163] gfs2: Fixes to "Implement iomap for block_map"

Greg Kroah-Hartman
2018-02-21T12:48:22Z

From: Andreas Gruenbacher <agruenba@redhat.com>

commit 49edd5bf429c405b3a7f75503845d9f66a47dd4b upstream.

It turns out that commit 3974320ca6 "Implement iomap for block_map"
introduced a few bugs that trigger occasional failures with xfstest
generic/476:

In gfs2_iomap_begin, we jump to do_alloc when we determine that we are
beyond the end of the allocated metadata (height > ip->i_height).
There, we can end up calling hole_size with a metapath that doesn't
match the current metadata tree, which doesn't make sense. After
untangling the code at do_alloc, fix this by checking if the block we
are looking for is within the range of allocated metadata.

In addition, add a BUG() in case gfs2_iomap_begin is accidentally called
for reading stuffed files: this is handled separately. Make sure we
don't truncate iomap->length for reads beyond the end of the file; in
that case, the entire range counts as a hole.

Finally, revert to taking a bitmap write lock when doing allocations.
It's unclear why that change didn't lead to any failures during testing.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/gfs2/bmap.c | 43 +++++++++++++++++++++++--------------------
1 file changed, 23 insertions(+), 20 deletions(-)

--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -736,7 +736,7 @@ int gfs2_iomap_begin(struct inode *inode
__be64 *ptr;
sector_t lblock;
sector_t lend;
- int ret;
+ int ret = 0;
int eob;
unsigned int len;
struct buffer_head *bh;
@@ -748,12 +748,14 @@ int gfs2_iomap_begin(struct inode *inode
goto out;
}

- if ((flags & IOMAP_REPORT) && gfs2_is_stuffed(ip)) {
- gfs2_stuffed_iomap(inode, iomap);
- if (pos >= iomap->length)
- return -ENOENT;
- ret = 0;
- goto out;
+ if (gfs2_is_stuffed(ip)) {
+ if (flags & IOMAP_REPORT) {
+ gfs2_stuffed_iomap(inode, iomap);
+ if (pos >= iomap->length)
+ ret = -ENOENT;
+ goto out;
+ }
+ BUG_ON(!(flags & IOMAP_WRITE));
}

lblock = pos >> inode->i_blkbits;
@@ -764,7 +766,7 @@ int gfs2_iomap_begin(struct inode *inode
iomap->type = IOMAP_HOLE;
iomap->length = (u64)(lend - lblock) << inode->i_blkbits;
iomap->flags = IOMAP_F_MERGED;
- bmap_lock(ip, 0);
+ bmap_lock(ip, flags & IOMAP_WRITE);

/*
* Directory data blocks have a struct gfs2_meta_header header, so the
@@ -807,27 +809,28 @@ int gfs2_iomap_begin(struct inode *inode
iomap->flags |= IOMAP_F_BOUNDARY;
iomap->length = (u64)len << inode->i_blkbits;

- ret = 0;
-
out_release:
release_metapath(&mp);
- bmap_unlock(ip, 0);
+ bmap_unlock(ip, flags & IOMAP_WRITE);
out:
trace_gfs2_iomap_end(ip, iomap, ret);
return ret;

do_alloc:
- if (!(flags & IOMAP_WRITE)) {
- if (pos >= i_size_read(inode)) {
+ if (flags & IOMAP_WRITE) {
+ ret = gfs2_iomap_alloc(inode, iomap, flags, &mp);
+ } else if (flags & IOMAP_REPORT) {
+ loff_t size = i_size_read(inode);
+ if (pos >= size)
ret = -ENOENT;
- goto out_release;
- }
- ret = 0;
- iomap->length = hole_size(inode, lblock, &mp);
- goto out_release;
+ else if (height <= ip->i_height)
+ iomap->length = hole_size(inode, lblock, &mp);
+ else
+ iomap->length = size - pos;
+ } else {
+ if (height <= ip->i_height)
+ iomap->length = hole_size(inode, lblock, &mp);
}
-
- ret = gfs2_iomap_alloc(inode, iomap, flags, &mp);
goto out_release;
}