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SubjectRe: [PATCH] jffs2: remove fd from the f->dents list immediately.
Date
On Fri, 2018-03-16 at 19:05 +0800, Yufen Yu wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
>
> commit 15953580e79b ("[JFFS2] Improve getdents vs. f_pos handling on NOR flash.")
> is introduced to resolve 'rm -r', which cannot remove all files:
> http://lists.infradead.org/pipermail/linux-mtd/2007-October/019658.html
>
> However, it can cause the following issues:
>
> 1. 'deletion' dirents is alway in the f->dents list, wasting memory
> resource. For example:
> There is a file named 'file1'. Then we rename it:
> mv file1 file2;
> mv file2 file3;
> ...
> mv file99999 file1000000
>
> When CONFIG_JFFS2_SUMMARY is not set, file1~file1000000
> always in the f->dents list.
>
> 2. Since the list become longer and longer, more CPU time is used
> to traverse it.
>
> After reverting the commit, we test 'rm -r', which can remove all
> files, and all seems OK!

UHH, this is mine (and Davids work from 2007)!
I cannot remember any details this long afterwards but I guess you cannot just
revert that part as it triggers some other bug, David?

Jocke

>
> Signed-off-by: Yufen Yu <yuyufen@huawei.com>
> ---
> fs/jffs2/write.c | 33 +++++++++++++++++----------------
> 1 file changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/fs/jffs2/write.c b/fs/jffs2/write.c
> index cda9a361368e..1deed35beb50 100644
> --- a/fs/jffs2/write.c
> +++ b/fs/jffs2/write.c
> @@ -598,31 +598,32 @@ int jffs2_do_unlink(struct jffs2_sb_info *c, struct jffs2_inode_info *dir_f,
> jffs2_add_fd_to_list(c, fd, &dir_f->dents);
> mutex_unlock(&dir_f->sem);
> } else {
> + struct jffs2_full_dirent **prev = &dir_f->dents;
> uint32_t nhash = full_name_hash(NULL, name, namelen);
>
> - fd = dir_f->dents;
> /* We don't actually want to reserve any space, but we do
> want to be holding the alloc_sem when we write to flash */
> mutex_lock(&c->alloc_sem);
> mutex_lock(&dir_f->sem);
>
> - for (fd = dir_f->dents; fd; fd = fd->next) {
> - if (fd->nhash == nhash &&
> - !memcmp(fd->name, name, namelen) &&
> - !fd->name[namelen]) {
> -
> - jffs2_dbg(1, "Marking old dirent node (ino #%u) @%08x obsolete\n",
> - fd->ino, ref_offset(fd->raw));
> - jffs2_mark_node_obsolete(c, fd->raw);
> - /* We don't want to remove it from the list immediately,
> - because that screws up getdents()/seek() semantics even
> - more than they're screwed already. Turn it into a
> - node-less deletion dirent instead -- a placeholder */
> - fd->raw = NULL;
> - fd->ino = 0;
> - break;
> + while ((*prev) && (*prev)->nhash <= nhash) {
> + if ((*prev)->nhash == nhash &&
> + !memcmp((*prev)->name, name, namelen) &&
> + !(*prev)->name[namelen]) {
> +
> + struct jffs2_full_dirent *this = *prev;
> +
> + jffs2_dbg(1, "Marking old dirent node (ino #%u) @%08x obsolete\n",
> + this->ino, ref_offset(this->raw));
> + *prev = this->next;
> + jffs2_mark_node_obsolete(c, this->raw);
> + jffs2_free_full_dirent(this);
> +
> + break;
> }
> + prev = &((*prev)->next);
> }
> +
> mutex_unlock(&dir_f->sem);
> }
>
> --
> 2.13.6
>
>
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> http://lists.infradead.org/mailman/listinfo/linux-mtd/
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