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gfs2: Fixes to "Implement iomap for block_map"

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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>
This commit is contained in:
Andreas Gruenbacher 2018-02-06 07:20:55 -07:00 committed by Bob Peterson
parent 35277995e1
commit 49edd5bf42
1 changed files with 23 additions and 20 deletions
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43
fs/gfs2/bmap.c
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@ -716,7 +716,7 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
__be64 *ptr;
sector_t lblock;
sector_t lend;
int ret;
int ret = 0;
int eob;
unsigned int len;
struct buffer_head *bh;
@ -728,12 +728,14 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
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;
@ -744,7 +746,7 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
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
@ -787,27 +789,28 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
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;
}