Ceph has a following race between hole punching and page fault:
CPU1 CPU2
ceph_fallocate()
...
ceph_zero_pagecache_range()
ceph_filemap_fault()
faults in page in the range being
punched
ceph_zero_objects()
And now we have a page in punched range with invalid data. Fix the
problem by using mapping->invalidate_lock similarly to other
filesystems. Note that using invalidate_lock also fixes a similar race
wrt ->readpage().
CC: Jeff Layton <jlay...@kernel.org>
CC: ceph-de...@vger.kernel.org
Reviewed-by: Jeff Layton <jlay...@kernel.org>
Signed-off-by: Jan Kara <j...@suse.cz>
---
fs/ceph/addr.c | 9 ++++++---
fs/ceph/file.c | 2 ++
2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index a1e2813731d1..7e7a897ae0d3 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1395,9 +1395,11 @@ static vm_fault_t ceph_filemap_fault(struct vm_fault
*vmf)
ret = VM_FAULT_SIGBUS;
} else {
struct address_space *mapping = inode->i_mapping;
- struct page *page = find_or_create_page(mapping, 0,
- mapping_gfp_constraint(mapping,
- ~__GFP_FS));
+ struct page *page;
+
+ filemap_invalidate_lock_shared(mapping);
+ page = find_or_create_page(mapping, 0,
+ mapping_gfp_constraint(mapping, ~__GFP_FS));
if (!page) {
ret = VM_FAULT_OOM;
goto out_inline;
@@ -1418,6 +1420,7 @@ static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
vmf->page = page;
ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
out_inline:
+ filemap_invalidate_unlock_shared(mapping);
dout("filemap_fault %p %llu read inline data ret %x\n",
inode, off, ret);
}
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index d1755ac1d964..e1d605a02d4a 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -2088,6 +2088,7 @@ static long ceph_fallocate(struct file *file, int mode,
if (ret < 0)
goto unlock;
+ filemap_invalidate_lock(inode->i_mapping);
ceph_zero_pagecache_range(inode, offset, length);
ret = ceph_zero_objects(inode, offset, length);
@@ -2100,6 +2101,7 @@ static long ceph_fallocate(struct file *file, int mode,
if (dirty)
__mark_inode_dirty(inode, dirty);
}
+ filemap_invalidate_unlock(inode->i_mapping);
ceph_put_cap_refs(ci, got);
unlock:
--
2.26.2
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