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| author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-05-09 14:30:35 -0400 |
|---|---|---|
| committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-05-09 15:16:07 -0400 |
| commit | 3aff4ebb95b20ad8db2c1447e8c52097d89af5a7 (patch) | |
| tree | ad56aceafbcbd0650e71e029ffa138eedffd33ba | |
| parent | dc327ed4cd320be689596365372a3683208c3ba0 (diff) | |
| download | linux-3aff4ebb95b20ad8db2c1447e8c52097d89af5a7.tar.bz2 | |
NFS: Prevent a deadlock in the new writeback code
We have to unlock the nfs_page before we call nfs_end_page_writeback
to avoid races with functions that expect the page to be unlocked
when PG_locked and PG_writeback are not set.
The problem is that nfs_unlock_request also releases the nfs_page,
causing a deadlock if the release of the nfs_open_context
triggers an iput() while the PG_writeback flag is still set...
The solution is to separate the unlocking and release of the nfs_page,
so that we can do the former before nfs_end_page_writeback and the
latter after.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Fred Isaman <iisaman@netapp.com>
| -rw-r--r-- | fs/nfs/pagelist.c | 12 | ||||
| -rw-r--r-- | fs/nfs/write.c | 6 | ||||
| -rw-r--r-- | include/linux/nfs_page.h | 1 |
3 files changed, 15 insertions, 4 deletions
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index 33a21ca9b84b..69146f386989 100644 --- a/fs/nfs/pagelist.c +++ b/fs/nfs/pagelist.c @@ -128,10 +128,10 @@ nfs_create_request(struct nfs_open_context *ctx, struct inode *inode, } /** - * nfs_unlock_request - Unlock request and wake up sleepers. + * nfs_unlock_request_dont_release - Unlock request and wake up sleepers. * @req: */ -void nfs_unlock_request(struct nfs_page *req) +void nfs_unlock_request_dont_release(struct nfs_page *req) { if (!NFS_WBACK_BUSY(req)) { printk(KERN_ERR "NFS: Invalid unlock attempted\n"); @@ -141,6 +141,14 @@ void nfs_unlock_request(struct nfs_page *req) clear_bit(PG_BUSY, &req->wb_flags); smp_mb__after_clear_bit(); wake_up_bit(&req->wb_flags, PG_BUSY); +} + +/** + * nfs_unlock_request - Unlock request and release the nfs_page + */ +void nfs_unlock_request(struct nfs_page *req) +{ + nfs_unlock_request_dont_release(req); nfs_release_request(req); } diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 6f263daac748..fd36b31ee72e 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -628,8 +628,9 @@ static void nfs_write_completion(struct nfs_pgio_header *hdr) remove_req: nfs_inode_remove_request(req); next: - nfs_unlock_request(req); + nfs_unlock_request_dont_release(req); nfs_end_page_writeback(page); + nfs_release_request(req); } out: hdr->release(hdr); @@ -1042,8 +1043,9 @@ static void nfs_redirty_request(struct nfs_page *req) struct page *page = req->wb_page; nfs_mark_request_dirty(req); - nfs_unlock_request(req); + nfs_unlock_request_dont_release(req); nfs_end_page_writeback(page); + nfs_release_request(req); } static void nfs_async_write_error(struct list_head *head) diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h index f9ee9eba7f88..ef7504215446 100644 --- a/include/linux/nfs_page.h +++ b/include/linux/nfs_page.h @@ -96,6 +96,7 @@ extern bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *req); extern int nfs_wait_on_request(struct nfs_page *); extern void nfs_unlock_request(struct nfs_page *req); +extern void nfs_unlock_request_dont_release(struct nfs_page *req); /* * Lock the page of an asynchronous request without getting a new reference |