From: NeilBrown neilb@suse.de
[ Upstream commit 64158668ac8b31626a8ce48db4cad08496eb8340 ]
1/ Taking the i_rwsem for swap IO triggers lockdep warnings regarding possible deadlocks with "fs_reclaim". These deadlocks could, I believe, eventuate if a buffered read on the swapfile was attempted.
We don't need coherence with the page cache for a swap file, and buffered writes are forbidden anyway. There is no other need for i_rwsem during direct IO. So never take it for swap_rw()
2/ generic_write_checks() explicitly forbids writes to swap, and performs checks that are not needed for swap. So bypass it for swap_rw().
Signed-off-by: NeilBrown neilb@suse.de Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/direct.c | 42 ++++++++++++++++++++++++++++-------------- fs/nfs/file.c | 4 ++-- include/linux/nfs_fs.h | 8 ++++---- 3 files changed, 34 insertions(+), 20 deletions(-)
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index eabfdab543c8..04aaf39a05cb 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -173,8 +173,8 @@ ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
if (iov_iter_rw(iter) == READ) - return nfs_file_direct_read(iocb, iter); - return nfs_file_direct_write(iocb, iter); + return nfs_file_direct_read(iocb, iter, true); + return nfs_file_direct_write(iocb, iter, true); }
static void nfs_direct_release_pages(struct page **pages, unsigned int npages) @@ -425,6 +425,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, * nfs_file_direct_read - file direct read operation for NFS files * @iocb: target I/O control block * @iter: vector of user buffers into which to read data + * @swap: flag indicating this is swap IO, not O_DIRECT IO * * We use this function for direct reads instead of calling * generic_file_aio_read() in order to avoid gfar's check to see if @@ -440,7 +441,8 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, * client must read the updated atime from the server back into its * cache. */ -ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter) +ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter, + bool swap) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; @@ -482,12 +484,14 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter) if (iter_is_iovec(iter)) dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
- nfs_start_io_direct(inode); + if (!swap) + nfs_start_io_direct(inode);
NFS_I(inode)->read_io += count; requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
- nfs_end_io_direct(inode); + if (!swap) + nfs_end_io_direct(inode);
if (requested > 0) { result = nfs_direct_wait(dreq); @@ -876,6 +880,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, * nfs_file_direct_write - file direct write operation for NFS files * @iocb: target I/O control block * @iter: vector of user buffers from which to write data + * @swap: flag indicating this is swap IO, not O_DIRECT IO * * We use this function for direct writes instead of calling * generic_file_aio_write() in order to avoid taking the inode @@ -892,7 +897,8 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, * Note that O_APPEND is not supported for NFS direct writes, as there * is no atomic O_APPEND write facility in the NFS protocol. */ -ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) +ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter, + bool swap) { ssize_t result, requested; size_t count; @@ -906,7 +912,11 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n", file, iov_iter_count(iter), (long long) iocb->ki_pos);
- result = generic_write_checks(iocb, iter); + if (swap) + /* bypass generic checks */ + result = iov_iter_count(iter); + else + result = generic_write_checks(iocb, iter); if (result <= 0) return result; count = result; @@ -937,16 +947,20 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) dreq->iocb = iocb; pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
- nfs_start_io_direct(inode); + if (swap) { + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + } else { + nfs_start_io_direct(inode);
- requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos);
- if (mapping->nrpages) { - invalidate_inode_pages2_range(mapping, - pos >> PAGE_SHIFT, end); - } + if (mapping->nrpages) { + invalidate_inode_pages2_range(mapping, + pos >> PAGE_SHIFT, end); + }
- nfs_end_io_direct(inode); + nfs_end_io_direct(inode); + }
if (requested > 0) { result = nfs_direct_wait(dreq); diff --git a/fs/nfs/file.c b/fs/nfs/file.c index 76d76acbc594..d8583f57ff99 100644 --- a/fs/nfs/file.c +++ b/fs/nfs/file.c @@ -162,7 +162,7 @@ nfs_file_read(struct kiocb *iocb, struct iov_iter *to) ssize_t result;
if (iocb->ki_flags & IOCB_DIRECT) - return nfs_file_direct_read(iocb, to); + return nfs_file_direct_read(iocb, to, false);
dprintk("NFS: read(%pD2, %zu@%lu)\n", iocb->ki_filp, @@ -619,7 +619,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from) return result;
if (iocb->ki_flags & IOCB_DIRECT) - return nfs_file_direct_write(iocb, from); + return nfs_file_direct_write(iocb, from, false);
dprintk("NFS: write(%pD2, %zu@%Ld)\n", file, iov_iter_count(from), (long long) iocb->ki_pos); diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 68f81d8d36de..161e4f5ea7a0 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -513,10 +513,10 @@ static inline const struct cred *nfs_file_cred(struct file *file) * linux/fs/nfs/direct.c */ extern ssize_t nfs_direct_IO(struct kiocb *, struct iov_iter *); -extern ssize_t nfs_file_direct_read(struct kiocb *iocb, - struct iov_iter *iter); -extern ssize_t nfs_file_direct_write(struct kiocb *iocb, - struct iov_iter *iter); +ssize_t nfs_file_direct_read(struct kiocb *iocb, + struct iov_iter *iter, bool swap); +ssize_t nfs_file_direct_write(struct kiocb *iocb, + struct iov_iter *iter, bool swap);
/* * linux/fs/nfs/dir.c