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Date: Wed, 31 May 2023 15:18:28 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Jingbo Xu <jefflexu@...ux.alibaba.com>, xiang@...nel.org,
chao@...nel.org, huyue2@...lpad.com, linux-erofs@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 5/5] erofs: use separate xattr parsers for
listxattr/getxattr
On 2023/5/31 11:13, Jingbo Xu wrote:
> There's a callback styled xattr parser, i.e. xattr_foreach(), which is
> shared among listxattr and getxattr. Convert it to two separate xattr
> parsers for listxattr and getxattr.
>
> Signed-off-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
> ---
> fs/erofs/xattr.c | 372 ++++++++++++++++++++---------------------------
> 1 file changed, 155 insertions(+), 217 deletions(-)
>
> diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
> index 074743e2b271..438fcf22b230 100644
> --- a/fs/erofs/xattr.c
> +++ b/fs/erofs/xattr.c
> @@ -12,7 +12,7 @@ struct erofs_xattr_iter {
> struct erofs_buf buf;
> void *kaddr;
> erofs_blk_t blkaddr;
> - unsigned int ofs;
> + unsigned int ofs, next_ofs;
>
> char *buffer;
> int buffer_size, buffer_ofs;
> @@ -141,183 +141,6 @@ static int erofs_init_inode_xattrs(struct inode *inode)
> return ret;
> }
>
> -/*
> - * the general idea for these return values is
> - * if 0 is returned, go on processing the current xattr;
> - * 1 (> 0) is returned, skip this round to process the next xattr;
> - * -err (< 0) is returned, an error (maybe ENOXATTR) occurred
> - * and need to be handled
> - */
> -struct xattr_iter_handlers {
> - int (*entry)(struct erofs_xattr_iter *it, struct erofs_xattr_entry *entry);
> - int (*name)(struct erofs_xattr_iter *it, unsigned int processed, char *buf,
> - unsigned int len);
> - int (*alloc_buffer)(struct erofs_xattr_iter *it, unsigned int value_sz);
> - void (*value)(struct erofs_xattr_iter *it, unsigned int processed, char *buf,
> - unsigned int len);
> -};
> -
> -/*
> - * Regardless of success or failure, `xattr_foreach' will end up with
> - * `ofs' pointing to the next xattr item rather than an arbitrary position.
> - */
> -static int xattr_foreach(struct erofs_xattr_iter *it,
> - const struct xattr_iter_handlers *op,
> - unsigned int *tlimit)
> -{
> - struct erofs_xattr_entry entry;
> - unsigned int value_sz, processed, slice;
> - int err;
> -
> - /* 0. fixup blkaddr, ofs, ipage */
> - err = erofs_xattr_iter_fixup(it, false);
> - if (err)
> - return err;
> -
> - /*
> - * 1. read xattr entry to the memory,
> - * since we do EROFS_XATTR_ALIGN
> - * therefore entry should be in the page
> - */
> - entry = *(struct erofs_xattr_entry *)(it->kaddr + it->ofs);
> - if (tlimit) {
> - unsigned int entry_sz = erofs_xattr_entry_size(&entry);
> -
> - /* xattr on-disk corruption: xattr entry beyond xattr_isize */
> - if (*tlimit < entry_sz) {
> - DBG_BUGON(1);
> - return -EFSCORRUPTED;
> - }
> - *tlimit -= entry_sz;
> - }
> -
> - it->ofs += sizeof(struct erofs_xattr_entry);
> - value_sz = le16_to_cpu(entry.e_value_size);
> -
> - /* handle entry */
> - err = op->entry(it, &entry);
> - if (err) {
> - it->ofs += entry.e_name_len + value_sz;
> - goto out;
> - }
> -
> - /* 2. handle xattr name (ofs will finally be at the end of name) */
> - processed = 0;
> -
> - while (processed < entry.e_name_len) {
> - err = erofs_xattr_iter_fixup(it, true);
> - if (err)
> - goto out;
> -
> - slice = min_t(unsigned int, it->sb->s_blocksize - it->ofs,
> - entry.e_name_len - processed);
> -
> - /* handle name */
> - err = op->name(it, processed, it->kaddr + it->ofs, slice);
> - if (err) {
> - it->ofs += entry.e_name_len - processed + value_sz;
> - goto out;
> - }
> -
> - it->ofs += slice;
> - processed += slice;
> - }
> -
> - /* 3. handle xattr value */
> - processed = 0;
> -
> - if (op->alloc_buffer) {
> - err = op->alloc_buffer(it, value_sz);
> - if (err) {
> - it->ofs += value_sz;
> - goto out;
> - }
> - }
> -
> - while (processed < value_sz) {
> - err = erofs_xattr_iter_fixup(it, true);
> - if (err)
> - goto out;
> -
> - slice = min_t(unsigned int, it->sb->s_blocksize - it->ofs,
> - value_sz - processed);
> - op->value(it, processed, it->kaddr + it->ofs, slice);
> - it->ofs += slice;
> - processed += slice;
> - }
> -
> -out:
> - /* xattrs should be 4-byte aligned (on-disk constraint) */
> - it->ofs = EROFS_XATTR_ALIGN(it->ofs);
> - return err < 0 ? err : 0;
> -}
> -
> -static int erofs_xattr_long_entrymatch(struct erofs_xattr_iter *it,
> - struct erofs_xattr_entry *entry)
> -{
> - struct erofs_sb_info *sbi = EROFS_SB(it->sb);
> - struct erofs_xattr_prefix_item *pf = sbi->xattr_prefixes +
> - (entry->e_name_index & EROFS_XATTR_LONG_PREFIX_MASK);
> -
> - if (pf >= sbi->xattr_prefixes + sbi->xattr_prefix_count)
> - return -ENOATTR;
> -
> - if (it->index != pf->prefix->base_index ||
> - it->name.len != entry->e_name_len + pf->infix_len)
> - return -ENOATTR;
> -
> - if (memcmp(it->name.name, pf->prefix->infix, pf->infix_len))
> - return -ENOATTR;
> -
> - it->infix_len = pf->infix_len;
> - return 0;
> -}
> -
> -static int xattr_entrymatch(struct erofs_xattr_iter *it,
> - struct erofs_xattr_entry *entry)
> -{
> - /* should also match the infix for long name prefixes */
> - if (entry->e_name_index & EROFS_XATTR_LONG_PREFIX)
> - return erofs_xattr_long_entrymatch(it, entry);
> -
> - if (it->index != entry->e_name_index ||
> - it->name.len != entry->e_name_len)
> - return -ENOATTR;
> - it->infix_len = 0;
> - return 0;
> -}
> -
> -static int xattr_namematch(struct erofs_xattr_iter *it,
> - unsigned int processed, char *buf, unsigned int len)
> -{
> - if (memcmp(buf, it->name.name + it->infix_len + processed, len))
> - return -ENOATTR;
> - return 0;
> -}
> -
> -static int xattr_checkbuffer(struct erofs_xattr_iter *it,
> - unsigned int value_sz)
> -{
> - int err = it->buffer_size < value_sz ? -ERANGE : 0;
> -
> - it->buffer_ofs = value_sz;
> - return !it->buffer ? 1 : err;
> -}
> -
> -static void xattr_copyvalue(struct erofs_xattr_iter *it,
> - unsigned int processed,
> - char *buf, unsigned int len)
> -{
> - memcpy(it->buffer + processed, buf, len);
> -}
> -
> -static const struct xattr_iter_handlers find_xattr_handlers = {
> - .entry = xattr_entrymatch,
> - .name = xattr_namematch,
> - .alloc_buffer = xattr_checkbuffer,
> - .value = xattr_copyvalue
> -};
> -
> static bool erofs_xattr_user_list(struct dentry *dentry)
> {
> return test_opt(&EROFS_SB(dentry->d_sb)->opt, XATTR_USER);
> @@ -370,20 +193,70 @@ const struct xattr_handler *erofs_xattr_handlers[] = {
> NULL,
> };
>
> -static int xattr_entrylist(struct erofs_xattr_iter *it,
> - struct erofs_xattr_entry *entry)
> +typedef int (*erofs_xattr_body_handler)(struct erofs_xattr_iter *it,
> + unsigned int processed, char *buf, unsigned int len);
> +
> +static int erofs_xattr_namematch(struct erofs_xattr_iter *it,
> + unsigned int processed, char *buf, unsigned int len)
> +{
> + if (memcmp(buf, it->name.name + it->infix_len + processed, len))
> + return -ENOATTR;
> + return 0;
> +}
> +
> +static int erofs_xattr_copy(struct erofs_xattr_iter *it,
> + unsigned int unused, char *buf, unsigned int len)
> +{
> + memcpy(it->buffer + it->buffer_ofs, buf, len);
> + it->buffer_ofs += len;
> + return 0;
> +}
> +
> +static int erofs_xattr_body(struct erofs_xattr_iter *it, unsigned int len,
> + erofs_xattr_body_handler handler)
could we change erofs_xattr_body_handler into a bool (e.g.
bool copy_or_match)?
> +{
> + unsigned int slice, processed = 0;
> +
> + while (processed < len) {
> + int err = erofs_xattr_iter_fixup(it, true);
> + if (err)
> + return err;
> +
> + slice = min_t(unsigned int, it->sb->s_blocksize - it->ofs,
> + len - processed);
> + err = handler(it, processed, it->kaddr + it->ofs, slice);
So that an indirect call could be avoided, as:
if (copy_or_match) {
memcpy(it->buffer + it->buffer_ofs, buf, len);
it->buffer_ofs += len;
} else if (memcmp(buf,
it->name.name + it->infix_len + processed, len)) {
return -ENOATTR;
}
?
Thanks,
Gao Xiang
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