Re: [PATCH 30/31] ext4: eliminate xattr entry e_hash recalculation for removes

From: Jan Kara
Date: Thu Jun 15 2017 - 05:10:40 EST

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In reply to: Tahsin Erdogan: "[PATCH 30/31] ext4: eliminate xattr entry e_hash recalculation for removes"
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On Wed 14-06-17 10:23:40, Tahsin Erdogan wrote:
> When an extended attribute block is modified, ext4_xattr_hash_entry()
> recalculates e_hash for the entry that is pointed by s->here. This is
> unnecessary if the modification is to remove an entry.
>
> Currently, if the removed entry is the last one and there are other
> entries remaining, hash calculation targets the just erased entry which
> has been filled with zeroes and effectively does nothing. If the removed
> entry is not the last one and there are more entries, this time it will
> recalculate hash on the next entry which is totally unnecessary.
>
> Fix these by moving the decision on when to recalculate hash to
> ext4_xattr_set_entry().

I agree with moving ext4_xattr_rehash_entry() out of ext4_xattr_rehash().
However how about just keeping ext4_xattr_rehash() in
ext4_xattr_block_set() (so that you don't have to pass aditional argument
to ext4_xattr_set_entry()) and calling ext4_xattr_rehash_entry() when
i->value != NULL? That would seem easier and cleaner as well...

Honza
>
> Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
> ---
> fs/ext4/xattr.c | 50 ++++++++++++++++++++++++++------------------------
> 1 file changed, 26 insertions(+), 24 deletions(-)
>
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index c9579d220a0c..6c6dce2f874e 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -77,8 +77,9 @@ static void ext4_xattr_block_cache_insert(struct mb_cache *,
> static struct buffer_head *
> ext4_xattr_block_cache_find(struct inode *, struct ext4_xattr_header *,
> struct mb_cache_entry **);
> -static void ext4_xattr_rehash(struct ext4_xattr_header *,
> - struct ext4_xattr_entry *);
> +static void ext4_xattr_hash_entry(struct ext4_xattr_entry *entry,
> + void *value_base);
> +static void ext4_xattr_rehash(struct ext4_xattr_header *);
>
> static const struct xattr_handler * const ext4_xattr_handler_map[] = {
> [EXT4_XATTR_INDEX_USER] = &ext4_xattr_user_handler,
> @@ -1436,7 +1437,8 @@ static int ext4_xattr_inode_lookup_create(handle_t *handle, struct inode *inode,
>
> static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
> struct ext4_xattr_search *s,
> - handle_t *handle, struct inode *inode)
> + handle_t *handle, struct inode *inode,
> + bool is_block)
> {
> struct ext4_xattr_entry *last;
> struct ext4_xattr_entry *here = s->here;
> @@ -1500,8 +1502,8 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
> * attribute block so that a long value does not occupy the
> * whole space and prevent futher entries being added.
> */
> - if (ext4_has_feature_ea_inode(inode->i_sb) && new_size &&
> - (s->end - s->base) == i_blocksize(inode) &&
> + if (ext4_has_feature_ea_inode(inode->i_sb) &&
> + new_size && is_block &&
> (min_offs + old_size - new_size) <
> EXT4_XATTR_BLOCK_RESERVE(inode)) {
> ret = -ENOSPC;
> @@ -1631,6 +1633,13 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
> }
> here->e_value_size = cpu_to_le32(i->value_len);
> }
> +
> + if (is_block) {
> + if (s->not_found || i->value)
> + ext4_xattr_hash_entry(here, s->base);
> + ext4_xattr_rehash((struct ext4_xattr_header *)s->base);
> + }
> +
> ret = 0;
> out:
> iput(old_ea_inode);
> @@ -1720,14 +1729,11 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
> mb_cache_entry_delete(ext4_mb_cache, hash,
> bs->bh->b_blocknr);
> ea_bdebug(bs->bh, "modifying in-place");
> - error = ext4_xattr_set_entry(i, s, handle, inode);
> - if (!error) {
> - if (!IS_LAST_ENTRY(s->first))
> - ext4_xattr_rehash(header(s->base),
> - s->here);
> + error = ext4_xattr_set_entry(i, s, handle, inode,
> + true /* is_block */);
> + if (!error)
> ext4_xattr_block_cache_insert(ext4_mb_cache,
> bs->bh);
> - }
> ext4_xattr_block_csum_set(inode, bs->bh);
> unlock_buffer(bs->bh);
> if (error == -EFSCORRUPTED)
> @@ -1787,7 +1793,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
> s->end = s->base + sb->s_blocksize;
> }
>
> - error = ext4_xattr_set_entry(i, s, handle, inode);
> + error = ext4_xattr_set_entry(i, s, handle, inode, true /* is_block */);
> if (error == -EFSCORRUPTED)
> goto bad_block;
> if (error)
> @@ -1810,9 +1816,6 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
> }
> }
>
> - if (!IS_LAST_ENTRY(s->first))
> - ext4_xattr_rehash(header(s->base), s->here);
> -
> inserted:
> if (!IS_LAST_ENTRY(s->first)) {
> new_bh = ext4_xattr_block_cache_find(inode, header(s->base),
> @@ -2045,7 +2048,7 @@ int ext4_xattr_ibody_inline_set(handle_t *handle, struct inode *inode,
>
> if (EXT4_I(inode)->i_extra_isize == 0)
> return -ENOSPC;
> - error = ext4_xattr_set_entry(i, s, handle, inode);
> + error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */);
> if (error) {
> if (error == -ENOSPC &&
> ext4_has_inline_data(inode)) {
> @@ -2057,7 +2060,8 @@ int ext4_xattr_ibody_inline_set(handle_t *handle, struct inode *inode,
> error = ext4_xattr_ibody_find(inode, i, is);
> if (error)
> return error;
> - error = ext4_xattr_set_entry(i, s, handle, inode);
> + error = ext4_xattr_set_entry(i, s, handle, inode,
> + false /* is_block */);
> }
> if (error)
> return error;
> @@ -2083,7 +2087,7 @@ static int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
>
> if (EXT4_I(inode)->i_extra_isize == 0)
> return -ENOSPC;
> - error = ext4_xattr_set_entry(i, s, handle, inode);
> + error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */);
> if (error)
> return error;
> header = IHDR(inode, ext4_raw_inode(&is->iloc));
> @@ -2909,8 +2913,8 @@ ext4_xattr_block_cache_find(struct inode *inode,
> *
> * Compute the hash of an extended attribute.
> */
> -static inline void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
> - struct ext4_xattr_entry *entry)
> +static void ext4_xattr_hash_entry(struct ext4_xattr_entry *entry,
> + void *value_base)
> {
> __u32 hash = 0;
> char *name = entry->e_name;
> @@ -2923,7 +2927,7 @@ static inline void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
> }
>
> if (!entry->e_value_inum && entry->e_value_size) {
> - __le32 *value = (__le32 *)((char *)header +
> + __le32 *value = (__le32 *)((char *)value_base +
> le16_to_cpu(entry->e_value_offs));
> for (n = (le32_to_cpu(entry->e_value_size) +
> EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
> @@ -2945,13 +2949,11 @@ static inline void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
> *
> * Re-compute the extended attribute hash value after an entry has changed.
> */
> -static void ext4_xattr_rehash(struct ext4_xattr_header *header,
> - struct ext4_xattr_entry *entry)
> +static void ext4_xattr_rehash(struct ext4_xattr_header *header)
> {
> struct ext4_xattr_entry *here;
> __u32 hash = 0;
>
> - ext4_xattr_hash_entry(header, entry);
> here = ENTRY(header+1);
> while (!IS_LAST_ENTRY(here)) {
> if (!here->e_hash) {
> --
> 2.13.1.508.gb3defc5cc-goog
>
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR

Next message: Peter Chen: "Re: [PATCH v15 2/7] power: add power sequence library"
Previous message: Srinath Mannam: "[PATCH] usb: gadget: bdc: 64-bit pointer capability check"
In reply to: Tahsin Erdogan: "[PATCH 30/31] ext4: eliminate xattr entry e_hash recalculation for removes"
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