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authorDarrick J. Wong <darrick.wong@oracle.com>2017-01-25 20:24:57 -0800
committerDarrick J. Wong <darrick.wong@oracle.com>2017-01-25 20:24:57 -0800
commit2aa6ba7b5ad3189cc27f14540aa2f57f0ed8df4b (patch)
treec0974c14d598d72615b4e46f2ecb0e020d24efd0
parent493611ebd62673f39e2f52c2561182c558a21cb6 (diff)
xfs: clear _XBF_PAGES from buffers when readahead page
If we try to allocate memory pages to back an xfs_buf that we're trying to read, it's possible that we'll be so short on memory that the page allocation fails. For a blocking read we'll just wait, but for readahead we simply dump all the pages we've collected so far. Unfortunately, after dumping the pages we neglect to clear the _XBF_PAGES state, which means that the subsequent call to xfs_buf_free thinks that b_pages still points to pages we own. It then double-frees the b_pages pages. This results in screaming about negative page refcounts from the memory manager, which xfs oughtn't be triggering. To reproduce this case, mount a filesystem where the size of the inodes far outweighs the availalble memory (a ~500M inode filesystem on a VM with 300MB memory did the trick here) and run bulkstat in parallel with other memory eating processes to put a huge load on the system. The "check summary" phase of xfs_scrub also works for this purpose. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Eric Sandeen <sandeen@redhat.com>
-rw-r--r--fs/xfs/xfs_buf.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 7f0a01f7b592..ac3b4db519df 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -422,6 +422,7 @@ retry:
out_free_pages:
for (i = 0; i < bp->b_page_count; i++)
__free_page(bp->b_pages[i]);
+ bp->b_flags &= ~_XBF_PAGES;
return error;
}