From: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
To: Trond Myklebust <trondmy@gmail.com>
Cc: linux-nfs <linux-nfs@vger.kernel.org>,
zhangliguang <zhangliguang@linux.alibaba.com>
Subject: Re: [PATCH 1/3] NFS: Fix off-by-one errors in nfs_readdir
Date: Sun, 7 Jul 2019 23:01:25 +0200 (CEST) [thread overview]
Message-ID: <1898309819.16314811.1562533285002.JavaMail.zimbra@desy.de> (raw)
In-Reply-To: <20190706185252.32488-1-trond.myklebust@hammerspace.com>
Hi Trond,
Unfortunately, this change doesn't fix another issue introduced
with be4c2d4723a4: en extra READDIR request after server have sent
all entries and indicated it with eol=true:
https://www.spinics.net/lists/linux-nfs/msg73399.html
Tigran.
----- Original Message -----
> From: "Trond Myklebust" <trondmy@gmail.com>
> To: "linux-nfs" <linux-nfs@vger.kernel.org>
> Cc: "zhangliguang" <zhangliguang@linux.alibaba.com>
> Sent: Saturday, July 6, 2019 8:52:50 PM
> Subject: [PATCH 1/3] NFS: Fix off-by-one errors in nfs_readdir
> In C, the array size and the maximum index are not the same. In this
> case, the field desc->pvec.nr is being used as a cursor but is
> occasionally being treated as if it the array size.
> This patch renames it to desc->pvec.cursor in order to make clear that
> it is tracking an index.
>
> Fixes: be4c2d4723a4 ("NFS: readdirplus optimization by cache mechanism")
> Cc: Liguang Zhang <zhangliguang@linux.alibaba.com>
> Cc: stable@vger.kernel.org # v5.1+
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
> fs/nfs/dir.c | 53 +++++++++++++++++++++++++---------------------------
> 1 file changed, 25 insertions(+), 28 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 57b6a45576ad..e44f3c9fad5b 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -134,14 +134,14 @@ struct nfs_cache_array_entry {
> };
>
> struct nfs_cache_array {
> - int size;
> - int eof_index;
> u64 last_cookie;
> + unsigned int size;
> + bool eof;
> struct nfs_cache_array_entry array[0];
> };
>
> struct readdirvec {
> - unsigned long nr;
> + unsigned long cursor;
> unsigned long index;
> struct page *pages[NFS_MAX_READDIR_RAPAGES];
> };
> @@ -172,7 +172,7 @@ static
> void nfs_readdir_clear_array(struct page *page)
> {
> struct nfs_cache_array *array;
> - int i;
> + unsigned int i;
>
> array = kmap_atomic(page);
> for (i = 0; i < array->size; i++)
> @@ -224,7 +224,7 @@ int nfs_readdir_add_to_array(struct nfs_entry *entry, struct
> page *page)
> array->last_cookie = entry->cookie;
> array->size++;
> if (entry->eof != 0)
> - array->eof_index = array->size;
> + array->eof = true;
> out:
> kunmap(page);
> return ret;
> @@ -239,7 +239,7 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array
> *array, nfs_readdir_descri
> if (diff < 0)
> goto out_eof;
> if (diff >= array->size) {
> - if (array->eof_index >= 0)
> + if (array->eof)
> goto out_eof;
> return -EAGAIN;
> }
> @@ -265,7 +265,7 @@ nfs_readdir_inode_mapping_valid(struct nfs_inode *nfsi)
> static
> int nfs_readdir_search_for_cookie(struct nfs_cache_array *array,
> nfs_readdir_descriptor_t *desc)
> {
> - int i;
> + unsigned int i;
> loff_t new_pos;
> int status = -EAGAIN;
>
> @@ -300,7 +300,7 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array
> *array, nfs_readdir_des
> return 0;
> }
> }
> - if (array->eof_index >= 0) {
> + if (array->eof) {
> status = -EBADCOOKIE;
> if (*desc->dir_cookie == array->last_cookie)
> desc->eof = true;
> @@ -532,10 +532,9 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc,
> struct nfs_entry *en
> struct nfs_cache_array *array;
> unsigned int count = 0;
> int status;
> - int max_rapages = NFS_MAX_READDIR_RAPAGES;
>
> desc->pvec.index = desc->page_index;
> - desc->pvec.nr = 0;
> + desc->pvec.cursor = 0;
>
> scratch = alloc_page(GFP_KERNEL);
> if (scratch == NULL)
> @@ -560,12 +559,12 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t
> *desc, struct nfs_entry *en
> if (desc->plus)
> nfs_prime_dcache(file_dentry(desc->file), entry);
>
> - status = nfs_readdir_add_to_array(entry, desc->pvec.pages[desc->pvec.nr]);
> + status = nfs_readdir_add_to_array(entry,
> desc->pvec.pages[desc->pvec.cursor]);
> if (status == -ENOSPC) {
> - desc->pvec.nr++;
> - if (desc->pvec.nr == max_rapages)
> + if (desc->pvec.cursor == ARRAY_SIZE(desc->pvec.pages) - 1)
> break;
> - status = nfs_readdir_add_to_array(entry, desc->pvec.pages[desc->pvec.nr]);
> + desc->pvec.cursor++;
> + status = nfs_readdir_add_to_array(entry,
> desc->pvec.pages[desc->pvec.cursor]);
> }
> if (status != 0)
> break;
> @@ -579,8 +578,8 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc,
> struct nfs_entry *en
>
> out_nopages:
> if (count == 0 || (status == -EBADCOOKIE && entry->eof != 0)) {
> - array = kmap_atomic(desc->pvec.pages[desc->pvec.nr]);
> - array->eof_index = array->size;
> + array = kmap_atomic(desc->pvec.pages[desc->pvec.cursor]);
> + array->eof = true;
> status = 0;
> kunmap_atomic(array);
> }
> @@ -588,11 +587,11 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t
> *desc, struct nfs_entry *en
> put_page(scratch);
>
> /*
> - * desc->pvec.nr > 0 means at least one page was completely filled,
> + * desc->pvec.cursor > 0 means at least one page was completely filled,
> * we should return -ENOSPC. Otherwise function
> * nfs_readdir_xdr_to_array will enter infinite loop.
> */
> - if (desc->pvec.nr > 0)
> + if (desc->pvec.cursor > 0)
> return -ENOSPC;
> return status;
> }
> @@ -634,13 +633,12 @@ static
> void nfs_readdir_rapages_init(nfs_readdir_descriptor_t *desc)
> {
> struct nfs_cache_array *array;
> - int max_rapages = NFS_MAX_READDIR_RAPAGES;
> - int index;
> + unsigned int max_rapages = NFS_MAX_READDIR_RAPAGES;
> + unsigned int index;
>
> for (index = 0; index < max_rapages; index++) {
> array = kmap_atomic(desc->pvec.pages[index]);
> memset(array, 0, sizeof(struct nfs_cache_array));
> - array->eof_index = -1;
> kunmap_atomic(array);
> }
> }
> @@ -678,7 +676,6 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc,
> struct page *page,
>
> array = kmap(page);
> memset(array, 0, sizeof(struct nfs_cache_array));
> - array->eof_index = -1;
>
> status = nfs_readdir_alloc_pages(pages, array_size);
> if (status < 0)
> @@ -696,7 +693,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc,
> struct page *page,
> status = 0;
> break;
> }
> - } while (array->eof_index < 0);
> + } while (!array->eof);
>
> nfs_readdir_free_pages(pages, array_size);
> out_release_array:
> @@ -723,10 +720,10 @@ int nfs_readdir_filler(void *data, struct page* page)
>
> /*
> * If desc->page_index in range desc->pvec.index and
> - * desc->pvec.index + desc->pvec.nr, we get readdir cache hit.
> + * desc->pvec.index + desc->pvec.cursor, we get readdir cache hit.
> */
> if (desc->page_index >= desc->pvec.index &&
> - desc->page_index < (desc->pvec.index + desc->pvec.nr)) {
> + desc->page_index <= (desc->pvec.index + desc->pvec.cursor)) {
> /*
> * page and desc->pvec.pages[x] are valid, don't need to check
> * whether or not to be NULL.
> @@ -809,7 +806,7 @@ static
> int nfs_do_filldir(nfs_readdir_descriptor_t *desc)
> {
> struct file *file = desc->file;
> - int i = 0;
> + unsigned int i = 0;
> int res = 0;
> struct nfs_cache_array *array = NULL;
> struct nfs_open_dir_context *ctx = file->private_data;
> @@ -832,7 +829,7 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc)
> if (ctx->duped != 0)
> ctx->duped = 1;
> }
> - if (array->eof_index >= 0)
> + if (array->eof)
> desc->eof = true;
>
> kunmap(desc->page);
> @@ -903,7 +900,7 @@ static int nfs_readdir(struct file *file, struct dir_context
> *ctx)
> *desc = &my_desc;
> struct nfs_open_dir_context *dir_ctx = file->private_data;
> int res = 0;
> - int max_rapages = NFS_MAX_READDIR_RAPAGES;
> + unsigned int max_rapages = NFS_MAX_READDIR_RAPAGES;
>
> dfprintk(FILE, "NFS: readdir(%pD2) starting at cookie %llu\n",
> file, (long long)ctx->pos);
> --
> 2.21.0
prev parent reply other threads:[~2019-07-07 21:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-06 18:52 [PATCH 1/3] NFS: Fix off-by-one errors in nfs_readdir Trond Myklebust
2019-07-06 18:52 ` [PATCH 2/3] NFS: Reduce stack usage in nfs_readdir() Trond Myklebust
2019-07-06 18:52 ` [PATCH 3/3] NFS: Ensure cached readdir info is NUL terminated Trond Myklebust
2019-07-07 21:01 ` Mkrtchyan, Tigran [this message]
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