ext4: shortcut setting of xattr to the same value (3fd16462) · Commits · 戴 / test

When someone tried to set xattr to the same value (i.e., not changing anything) we did all the work of removing original xattr, possibly breaking references to shared xattr block, inserting new xattr, and merging xattr blocks again. Since this is not so rare operation and it is relatively cheap for us to detect this case, check for this and shortcut xattr setting in that case. Signed-off-by:

Jan Kara <jack@suse.cz> Signed-off-by:

Theodore Ts'o <tytso@mit.edu>

fs/ext4/xattr.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -1096,6 +1096,17 @@ static int ext4_xattr_ibody_set(handle_t handle, struct inode inode,
		return 0;
		}

		static int ext4_xattr_value_same(struct ext4_xattr_search *s,
		struct ext4_xattr_info *i)
		{
		void *value;

		if (le32_to_cpu(s->here->e_value_size) != i->value_len)
		return 0;
		value = ((void *)s->base) + le16_to_cpu(s->here->e_value_offs);
		return !memcmp(value, i->value, i->value_len);
		}

		/*
		* ext4_xattr_set_handle()
		*
		@@ -1172,6 +1183,13 @@ ext4_xattr_set_handle(handle_t handle, struct inode inode, int name_index,
		else if (!bs.s.not_found)
		error = ext4_xattr_block_set(handle, inode, &i, &bs);
		} else {
		error = 0;
		/* Xattr value did not change? Save us some work and bail out */
		if (!is.s.not_found && ext4_xattr_value_same(&is.s, &i))
		goto cleanup;
		if (!bs.s.not_found && ext4_xattr_value_same(&bs.s, &i))
		goto cleanup;

		error = ext4_xattr_ibody_set(handle, inode, &i, &is);
		if (!error && !bs.s.not_found) {
		i.value = NULL;

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