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authorSteven Whitehouse <swhiteho@redhat.com>2008-02-22 16:07:18 +0000
committerSteven Whitehouse <swhiteho@redhat.com>2008-03-31 10:41:12 +0100
commit7afd88d9166a752b52517648bcbe923e05d393fc (patch)
tree2fb945189e3cb1be7ad007088f8ec86e9f67ece6 /fs/gfs2/ops_address.c
parent60b779cfc1fa52034a996ee12a23b62d32e86000 (diff)
[GFS2] Fix a page lock / glock deadlock
We've previously been using a "try lock" in readpage on the basis that it would prevent deadlocks due to the inverted lock ordering (our normal lock ordering is glock first and then page lock). Unfortunately tests have shown that this isn't enough. If the glock has a demote request queued such that run_queue() in the glock code tries to do a demote when its called under readpage then it will try and write out all the dirty pages which requires locking them. This then deadlocks with the page locked by readpage. The solution is to always require two calls into readpage. The first unlocks the page, gets the glock and returns AOP_TRUNCATED_PAGE, the second does the actual readpage and unlocks the glock & page as required. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/ops_address.c')
-rw-r--r--fs/gfs2/ops_address.c27
1 files changed, 15 insertions, 12 deletions
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 7523999afc5..fbb4a6aa158 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -508,23 +508,26 @@ static int __gfs2_readpage(void *file, struct page *page)
static int gfs2_readpage(struct file *file, struct page *page)
{
struct gfs2_inode *ip = GFS2_I(page->mapping->host);
- struct gfs2_holder gh;
+ struct gfs2_holder *gh;
int error;
- gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);
- error = gfs2_glock_nq_atime(&gh);
- if (unlikely(error)) {
+ gh = gfs2_glock_is_locked_by_me(ip->i_gl);
+ if (!gh) {
+ gh = kmalloc(sizeof(struct gfs2_holder), GFP_NOFS);
+ if (!gh)
+ return -ENOBUFS;
+ gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME, gh);
unlock_page(page);
- goto out;
+ error = gfs2_glock_nq_atime(gh);
+ if (likely(error != 0))
+ goto out;
+ return AOP_TRUNCATED_PAGE;
}
error = __gfs2_readpage(file, page);
- gfs2_glock_dq(&gh);
+ gfs2_glock_dq(gh);
out:
- gfs2_holder_uninit(&gh);
- if (error == GLR_TRYFAILED) {
- yield();
- return AOP_TRUNCATED_PAGE;
- }
+ gfs2_holder_uninit(gh);
+ kfree(gh);
return error;
}
@@ -826,7 +829,7 @@ static int gfs2_write_end(struct file *file, struct address_space *mapping,
unsigned int to = from + len;
int ret;
- BUG_ON(gfs2_glock_is_locked_by_me(ip->i_gl) == 0);
+ BUG_ON(gfs2_glock_is_locked_by_me(ip->i_gl) == NULL);
ret = gfs2_meta_inode_buffer(ip, &dibh);
if (unlikely(ret)) {