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    SubjectRe: [regression] NFS readdir change break fully cached nfs root
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    Date
    On Tue, 2010-11-02 at 19:00 +0100, Andi Kleen wrote:
    > My NFS root test systems stopped booting with 2.6.37-rc1. It just
    > hangs after entering user space.
    >
    > The NFS root setup uses a slightly fancy parameter setup to minimize
    > network traffic:
    >
    > nfsroot=10.23.204.1:/home/nfsroot/edwin,nocto,acregmin=86400,acregmax=86400,acdirmin=86400,acdirmax=86400 root=/dev/nfs
    >
    > I bisected it down to this commit from Bryan.
    >
    > Unfortunately it's not trivially revertable because that conflicts
    > with later patches.

    Does the following patch help?

    Cheers
    Trond
    ------------------------------------------------------------------------
    NFS: Fix a couple of regressions in readdir.

    From: Trond Myklebust <Trond.Myklebust@netapp.com>

    Fix up the issue that array->eof_index needs to be able to be set
    even if array->size == 0.

    Ensure that we catch all important memory allocation error conditions
    and/or kmap() failures.

    Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
    ---

    fs/nfs/dir.c | 73 ++++++++++++++++++++++++++++++++++++++--------------------
    1 files changed, 48 insertions(+), 25 deletions(-)


    diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
    index 07ac384..8c22d60 100644
    --- a/fs/nfs/dir.c
    +++ b/fs/nfs/dir.c
    @@ -194,9 +194,13 @@ typedef struct {
    static
    struct nfs_cache_array *nfs_readdir_get_array(struct page *page)
    {
    + void *ptr;
    if (page == NULL)
    return ERR_PTR(-EIO);
    - return (struct nfs_cache_array *)kmap(page);
    + ptr = kmap(page);
    + if (ptr == NULL)
    + return ERR_PTR(-ENOMEM);
    + return ptr;
    }

    static
    @@ -213,6 +217,9 @@ int nfs_readdir_clear_array(struct page *page, gfp_t mask)
    {
    struct nfs_cache_array *array = nfs_readdir_get_array(page);
    int i;
    +
    + if (IS_ERR(array))
    + return PTR_ERR(array);
    for (i = 0; i < array->size; i++)
    kfree(array->array[i].string.name);
    nfs_readdir_release_array(page);
    @@ -244,7 +251,7 @@ int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)

    if (IS_ERR(array))
    return PTR_ERR(array);
    - ret = -EIO;
    + ret = -ENOSPC;
    if (array->size >= MAX_READDIR_ARRAY)
    goto out;

    @@ -255,9 +262,9 @@ int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
    if (ret)
    goto out;
    array->last_cookie = entry->cookie;
    + array->size++;
    if (entry->eof == 1)
    array->eof_index = array->size;
    - array->size++;
    out:
    nfs_readdir_release_array(page);
    return ret;
    @@ -272,7 +279,7 @@ 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_index >= 0)
    goto out_eof;
    desc->current_index += array->size;
    return -EAGAIN;
    @@ -281,8 +288,6 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri
    index = (unsigned int)diff;
    *desc->dir_cookie = array->array[index].cookie;
    desc->cache_entry_index = index;
    - if (index == array->eof_index)
    - desc->eof = 1;
    return 0;
    out_eof:
    desc->eof = 1;
    @@ -296,17 +301,17 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_des
    int status = -EAGAIN;

    for (i = 0; i < array->size; i++) {
    - if (i == array->eof_index) {
    - desc->eof = 1;
    - status = -EBADCOOKIE;
    - }
    if (array->array[i].cookie == *desc->dir_cookie) {
    desc->cache_entry_index = i;
    status = 0;
    - break;
    + goto out;
    }
    }
    -
    + if (i == array->eof_index) {
    + desc->eof = 1;
    + status = -EBADCOOKIE;
    + }
    +out:
    return status;
    }

    @@ -449,7 +454,7 @@ out:

    /* Perform conversion from xdr to cache array */
    static
    -void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
    +int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
    void *xdr_page, struct page *page, unsigned int buflen)
    {
    struct xdr_stream stream;
    @@ -471,21 +476,29 @@ void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *e

    do {
    status = xdr_decode(desc, entry, &stream);
    - if (status != 0)
    + if (status != 0) {
    + if (status == -EAGAIN)
    + status = 0;
    break;
    + }

    - if (nfs_readdir_add_to_array(entry, page) == -1)
    - break;
    if (desc->plus == 1)
    nfs_prime_dcache(desc->file->f_path.dentry, entry);
    +
    + status = nfs_readdir_add_to_array(entry, page);
    + if (status != 0)
    + break;
    } while (!entry->eof);

    if (status == -EBADCOOKIE && entry->eof) {
    array = nfs_readdir_get_array(page);
    - array->eof_index = array->size - 1;
    - status = 0;
    - nfs_readdir_release_array(page);
    + if (!IS_ERR(array)) {
    + array->eof_index = array->size;
    + status = 0;
    + nfs_readdir_release_array(page);
    + }
    }
    + return status;
    }

    static
    @@ -549,9 +562,14 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
    goto out;

    array = nfs_readdir_get_array(page);
    + if (IS_ERR(array)) {
    + status = PTR_ERR(array);
    + goto out;
    + }
    memset(array, 0, sizeof(struct nfs_cache_array));
    array->eof_index = -1;

    + status = -ENOMEM;
    pages_ptr = nfs_readdir_large_page(pages, array_size);
    if (!pages_ptr)
    goto out_release_array;
    @@ -560,8 +578,13 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,

    if (status < 0)
    break;
    - nfs_readdir_page_filler(desc, &entry, pages_ptr, page, array_size * PAGE_SIZE);
    - } while (array->eof_index < 0 && array->size < MAX_READDIR_ARRAY);
    + status = nfs_readdir_page_filler(desc, &entry, pages_ptr, page, array_size * PAGE_SIZE);
    + if (status < 0) {
    + if (status == -ENOSPC)
    + status = 0;
    + break;
    + }
    + } while (array->eof_index < 0);

    nfs_readdir_free_large_page(pages_ptr, pages, array_size);
    out_release_array:
    @@ -670,6 +693,8 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
    struct dentry *dentry = NULL;

    array = nfs_readdir_get_array(desc->page);
    + if (IS_ERR(array))
    + return PTR_ERR(array);

    for (i = desc->cache_entry_index; i < array->size; i++) {
    d_type = DT_UNKNOWN;
    @@ -685,11 +710,9 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
    *desc->dir_cookie = array->array[i+1].cookie;
    else
    *desc->dir_cookie = array->last_cookie;
    - if (i == array->eof_index) {
    - desc->eof = 1;
    - break;
    - }
    }
    + if (i == array->eof_index)
    + desc->eof = 1;

    nfs_readdir_release_array(desc->page);
    cache_page_release(desc);


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