Commit 227823d2 authored Jan 22, 2020 by Dai Ngo Committed by Anna Schumaker Feb 04, 2020

nfs: optimise readdir cache page invalidation



When the directory is large and it's being modified by one client
while another client is doing the 'ls -l' on the same directory then
the cache page invalidation from nfs_force_use_readdirplus causes
the reading client to keep restarting READDIRPLUS from cookie 0
which causes the 'ls -l' to take a very long time to complete,
possibly never completing.

Currently when nfs_force_use_readdirplus is called to switch from
READDIR to READDIRPLUS, it invalidates all the cached pages of the
directory. This cache page invalidation causes the next nfs_readdir
to re-read the directory content from cookie 0.

This patch is to optimise the cache invalidation in
nfs_force_use_readdirplus by only truncating the cached pages from
last page index accessed to the end the file. It also marks the
inode to delay invalidating all the cached page of the directory
until the next initial nfs_readdir of the next 'ls' instance.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Reviewed-by: Trond Myklebust <trond.myklebust@hammerspace.com>
[Anna - Fix conflicts with Trond's readdir patches]
[Anna - Remove redundant call to nfs_zap_mapping()]
[Anna - Replace d_inode(file_dentry(desc->file)) with file_inode(desc->file)]
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

parent 93a6ab7b

fs/nfs/dir.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -449,7 +449,8 @@ void nfs_force_use_readdirplus(struct inode *dir)
		if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
		!list_empty(&nfsi->open_files)) {
		set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags);
		invalidate_mapping_pages(dir->i_mapping, 0, -1);
		invalidate_mapping_pages(dir->i_mapping,
		nfsi->page_index + 1, -1);
		}
		}

		@@ -720,6 +721,8 @@ struct page get_cache_page(nfs_readdir_descriptor_t desc)
		static
		int find_and_lock_cache_page(nfs_readdir_descriptor_t *desc)
		{
		struct inode *inode = file_inode(desc->file);
		struct nfs_inode *nfsi = NFS_I(inode);
		int res;

		desc->page = get_cache_page(desc);
		@@ -731,9 +734,11 @@ int find_and_lock_cache_page(nfs_readdir_descriptor_t *desc)
		res = -EAGAIN;
		if (desc->page->mapping != NULL) {
		res = nfs_readdir_search_array(desc);
		if (res == 0)
		if (res == 0) {
		nfsi->page_index = desc->page_index;
		return 0;
		}
		}
		unlock_page(desc->page);
		error:
		cache_page_release(desc);

include/linux/nfs_fs.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -168,6 +168,9 @@ struct nfs_inode {
		struct rw_semaphore rmdir_sem;
		struct mutex commit_mutex;

		/* track last access to cached pages */
		unsigned long page_index;

		#if IS_ENABLED(CONFIG_NFS_V4)
		struct nfs4_cached_acl *nfs4_acl;
		/* NFSv4 state */

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