[PATCH 4.9 7/9] ceph: try getting buffer capability for readahead/fadvise

Greg Kroah-Hartman
2017-05-06T20:41:05Z

From: Yan, Zheng <zyan@redhat.com>

commit 2b1ac852eb67a6e95595e576371d23519105559f upstream.

For readahead/fadvise cases, caller of ceph_readpages does not
hold buffer capability. Pages can be added to page cache while
there is no buffer capability. This can cause data integrity
issue.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ceph/addr.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++----------
fs/ceph/caps.c | 21 ++++++++++++++++++++
fs/ceph/file.c | 3 +-
fs/ceph/super.h | 2 +
4 files changed, 73 insertions(+), 11 deletions(-)

--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -315,7 +315,32 @@ static int start_read(struct inode *inod
struct page **pages;
pgoff_t next_index;
int nr_pages = 0;
- int ret;
+ int got = 0;
+ int ret = 0;
+
+ if (!current->journal_info) {
+ /* caller of readpages does not hold buffer and read caps
+ * (fadvise, madvise and readahead cases) */
+ int want = CEPH_CAP_FILE_CACHE;
+ ret = ceph_try_get_caps(ci, CEPH_CAP_FILE_RD, want, &got);
+ if (ret < 0) {
+ dout("start_read %p, error getting cap\n", inode);
+ } else if (!(got & want)) {
+ dout("start_read %p, no cache cap\n", inode);
+ ret = 0;
+ }
+ if (ret <= 0) {
+ if (got)
+ ceph_put_cap_refs(ci, got);
+ while (!list_empty(page_list)) {
+ page = list_entry(page_list->prev,
+ struct page, lru);
+ list_del(&page->lru);
+ put_page(page);
+ }
+ return ret;
+ }
+ }

off = (u64) page_offset(page);

@@ -338,15 +363,18 @@ static int start_read(struct inode *inod
CEPH_OSD_FLAG_READ, NULL,
ci->i_truncate_seq, ci->i_truncate_size,
false);
- if (IS_ERR(req))
- return PTR_ERR(req);
+ if (IS_ERR(req)) {
+ ret = PTR_ERR(req);
+ goto out;
+ }

/* build page vector */
nr_pages = calc_pages_for(0, len);
pages = kmalloc(sizeof(*pages) * nr_pages, GFP_KERNEL);
- ret = -ENOMEM;
- if (!pages)
- goto out;
+ if (!pages) {
+ ret = -ENOMEM;
+ goto out_put;
+ }
for (i = 0; i < nr_pages; ++i) {
page = list_entry(page_list->prev, struct page, lru);
BUG_ON(PageLocked(page));
@@ -379,6 +407,12 @@ static int start_read(struct inode *inod
if (ret < 0)
goto out_pages;
ceph_osdc_put_request(req);
+
+ /* After adding locked pages to page cache, the inode holds cache cap.
+ * So we can drop our cap refs. */
+ if (got)
+ ceph_put_cap_refs(ci, got);
+
return nr_pages;

out_pages:
@@ -387,8 +421,11 @@ out_pages:
unlock_page(pages[i]);
}
ceph_put_page_vector(pages, nr_pages, false);
-out:
+out_put:
ceph_osdc_put_request(req);
+out:
+ if (got)
+ ceph_put_cap_refs(ci, got);
return ret;
}

@@ -425,7 +462,6 @@ static int ceph_readpages(struct file *f
rc = start_read(inode, page_list, max);
if (rc < 0)
goto out;
- BUG_ON(rc == 0);
}
out:
ceph_fscache_readpages_cancel(inode, page_list);
@@ -1372,9 +1408,11 @@ static int ceph_filemap_fault(struct vm_
inode, off, (size_t)PAGE_SIZE, ceph_cap_string(got));

if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
- ci->i_inline_version == CEPH_INLINE_NONE)
+ ci->i_inline_version == CEPH_INLINE_NONE) {
+ current->journal_info = vma->vm_file;
ret = filemap_fault(vma, vmf);
- else
+ current->journal_info = NULL;
+ } else
ret = -EAGAIN;

dout("filemap_fault %p %llu~%zd dropping cap refs on %s ret %d\n",
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2479,6 +2479,27 @@ static void check_max_size(struct inode
ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
}

+int ceph_try_get_caps(struct ceph_inode_info *ci, int need, int want, int *got)
+{
+ int ret, err = 0;
+
+ BUG_ON(need & ~CEPH_CAP_FILE_RD);
+ BUG_ON(want & ~(CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));
+ ret = ceph_pool_perm_check(ci, need);
+ if (ret < 0)
+ return ret;
+
+ ret = try_get_cap_refs(ci, need, want, 0, true, got, &err);
+ if (ret) {
+ if (err == -EAGAIN) {
+ ret = 0;
+ } else if (err < 0) {
+ ret = err;
+ }
+ }
+ return ret;
+}
+
/*
* Wait for caps, and take cap references. If we can't get a WR cap
* due to a small max_size, make sure we check_max_size (and possibly
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1249,8 +1249,9 @@ again:
dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
ceph_cap_string(got));
-
+ current->journal_info = filp;
ret = generic_file_read_iter(iocb, to);
+ current->journal_info = NULL;
}
dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -905,6 +905,8 @@ extern int ceph_encode_dentry_release(vo

extern int ceph_get_caps(struct ceph_inode_info *ci, int need, int want,
loff_t endoff, int *got, struct page **pinned_page);
+extern int ceph_try_get_caps(struct ceph_inode_info *ci,
+ int need, int want, int *got);

/* for counting open files by mode */
extern void __ceph_get_fmode(struct ceph_inode_info *ci, int mode);