On Wed, 2008-03-19 at 16:44 -0400, Trond Myklebust wrote:
> Please could you reverse the order of these two patches. I'd like to
> send this one in for 2.6.25, but I can't do that as long as it depends
> on the previous patch.
I ended up doing this myself, since I'd like to prepare this for merging
as soon as possible. Please could you ack the following updated patch.
Cheers
Trond
---------------------------------
From: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
Date: Wed, 19 Mar 2008 11:24:39 -0400
nfs: don't ignore return value from nfs_pageio_add_request
Ignoring the return value from nfs_pageio_add_request can cause deadlocks.
In read path:
call nfs_pageio_add_request from readpage_async_filler
assume at this point that there are requests already in desc, that
can't be merged with the current request.
so nfs_pageio_doio is fired up to clear out desc.
assume something goes wrong in setting up the io, so desc->pg_error is set.
This causes nfs_pageio_add_request to return 0, *WITHOUT* adding the original
request.
BUT, since return code is ignored, readpage_async_filler assumes it has
been added, and does nothing further, leaving page locked.
do_generic_mapping_read will eventually call lock_page, resulting in deadlock
In write path:
page is marked dirty by generic_perform_write
nfs_writepages is called
call nfs_pageio_add_request from nfs_page_async_flush
assume at this point that there are requests already in desc, that
can't be merged with the current request.
so nfs_pageio_doio is fired up to clear out desc.
assume something goes wrong in setting up the io, so desc->pg_error is set.
This causes nfs_page_async_flush to return 0, *WITHOUT* adding the original
request, yet marking the request as locked (PG_BUSY) and in writeback,
clearing dirty marks.
The next time a write is done to the page, deadlock will result as
nfs_write_end calls nfs_update_request
Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/read.c | 5 ++++-
fs/nfs/write.c | 8 +++++++-
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index be9e827..ab2f7d2 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -531,7 +531,10 @@ readpage_async_filler(void *data, struct page *page)
if (len < PAGE_CACHE_SIZE)
zero_user_segment(page, len, PAGE_CACHE_SIZE);
- nfs_pageio_add_request(desc->pgio, new);
+ if (!nfs_pageio_add_request(desc->pgio, new)) {
+ error = desc->pgio->pg_error;
+ goto out_unlock;
+ }
return 0;
out_error:
error = PTR_ERR(new);
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 3051302..7a2ba26 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -39,6 +39,7 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context*,
unsigned int, unsigned int);
static void nfs_pageio_init_write(struct nfs_pageio_descriptor *desc,
struct inode *inode, int ioflags);
+static void nfs_redirty_request(struct nfs_page *req);
static const struct rpc_call_ops nfs_write_partial_ops;
static const struct rpc_call_ops nfs_write_full_ops;
static const struct rpc_call_ops nfs_commit_ops;
@@ -279,7 +280,12 @@ static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
BUG();
}
spin_unlock(&inode->i_lock);
- nfs_pageio_add_request(pgio, req);
+ if (!nfs_pageio_add_request(pgio, req)) {
+ nfs_redirty_request(req);
+ nfs_end_page_writeback(page);
+ nfs_clear_page_tag_locked(req);
+ return pgio->pg_error;
+ }
return 0;
}
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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